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Lesson 4.2

Class Size:
How Big Should Classes Be?

Sure, California student-teacher ratios are high. But are they out of line?

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There's a limit to the amount of time and attention a teacher can give each student in their care. Class sizes vary dramatically among schools in different states and districts. It probably matters.

Class size in school systems is measured by the student-teacher ratio. In a small class there is more teacher-time available because it's allocated among fewer students. One strategy for improving educational quality is to hire more teachers, which lowers the student-teacher ratio. This lesson summarizes the arguments for and against making this change

California class sizes are huge

Compared to other states, class sizes in California are abnormally big.

Large class sizes, measured by comparing the number of students to the number of teachers on staff, are nothing new for California. The graph below shows the average student-teacher ratio in each state since 1970. In 2020, California ranked senond worst in the country for its student-to-teacher ratio in public schools, with 22.7 students per teacher.

The student-teacher ratio is used as a proxy for class size, but it isn't quite the same thing. Most actual class sizes are larger than this statewide benchmark because not all certified teachers at a school work in classes all day. Still, it is safe to say that the higher the number of students per teacher in a state in any given year, the larger class sizes must be, and vice versa.

Clearly, smaller classes cost more than big ones. But does it make a difference?

Smaller class size is better, but...

Like anything in social sciences, context matters. If all teachers were equally effective, then it would be obious: smaller class sizes are better. But teachers aren't all the same. Some thrive even with a large class. Other teachers struggle with larger classes, but might do better with smaller ones.

Research suggests that, on average, class sizes matter, especially in early grades and for disadvantaged students. But multi-national research by the Organization for Economic Cooperation and Development (OECD) concludes that other strategies for improvement might be better: "Overall, evidence on the effects of reduced class size on student performance is weak."

Virtually all research about class size finds that minor changes in the student-teacher ratio make no measurable difference. It’s not like a magic dial that immediately delivers better learning results with little adjustments. But California's class sizes are dramatically larger than those in most other states.

...the greatest benefits accrue for disadvantaged students in grades K-3, and when there are 18 or fewer students per teacher.

From the perspective of student outcomes, an ideal approach would optimize for classroom effectiveness, varying the size of classes according to how well individual teachers can accommodate them. This is a very difficult policy to put into a contract, though.

Class Size Matters, an advocacy organization, provides additional information and research on class sizes, including cost-benefit analyses.

Unintended consequences

In 1988, California voters passed Proposition 98, which required the California legislature to increase spending on public education. Then-governor George Deukmejian, who had opposed Prop 98, argued that a sudden influx of money would change nothing if it merely raised teacher salaries. As an alternative, he argued that the money should be invested in reducing class sizes for grades K-3, capping class size at twenty students.

This policy change had a strong basis in research, but it turned out badly. Implemented without a phase-in period, the mandate to reduce class sizes prompted a sudden boom in demand for K-3 teachers. As school districts rushed to fill the new teaching positions, experienced teachers had lots of schools to choose from. Unsurprisingly, they tended to choose positions in schools and districts that offered the best salaries and working conditions.

Schools serving low-income communities, meanwhile, had a hard time attracting qualified candidates. Smaller class sizes backfire if schools are forced to hire worse instructors. This disruption had a long-lasting and unequal impact on California's schools. It serves as a cautionary tale for education reform: beware unintended consequences.

The California Department of Finance estimates that the state spent over $22 billion on incentives for K-3 class size reduction from the program’s inception until it was changed in 2009-10. In the lean budget years leading to 2013, the incentives were reduced and the rules effectively eliminated. Elementary class sizes rose steadily as a result.

The Local Control Funding Formula, which defines how the state allocates funds to school districts, includes an incentive for districts to keep K-3 class sizes below 24 students. (Learn more about LCFF in Lesson 8.5)

Should classes vary in size?

In virtually any school, the number of students in each class tends to be pretty uniform. Walk into two 4th grade classrooms in a school district at random, and the number of students will probably vary little. Is this uniformity a mistake? Should classes vary in size?

Under the Local Control Funding Formula, which provides extra money for high-need students, local school districts have the power to vary class sizes if they want to, for example by reducing class sizes in schools that serve the highest proportions of low-income students or English learners. Research undertaken for the Getting Down to Facts II project identified this as a promising practice.

School time varies a great deal among the states and around the world. The next lesson, 4.3: School Hours, takes up the question of how much time students spend learning.

This lesson was updated in November 2023.


Which ONE of the following statements is TRUE?

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Questions & Comments

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user avatar
Carol Kocivar June 13, 2022 at 8:28 pm
California Education Code (EC) sections 41376 and 41378 prescribe the maximum class sizes and penalties for districts with any classes that exceed the limits established in 1964.

Kindergarten—average class size not to exceed 31 students; no class larger than 33 students
Grades one through three—average class size not to exceed 30 students; no class larger than 32 students
Grades four through eight—in the current fiscal year, average number of students per teacher not to exceed the greater of 29.9 (the statewide average number of students per teacher in 1964) or the district’s average number of students per teacher in 1964
user avatar
Sheila Melo May 29, 2020 at 11:03 am
One size doesn't fit all. Some classes can be larger and some classes or student populations need to be smaller. One kid attended private Catholic school with larger classes but because of the student population, it wasn't a problem to have classes with 35 kids and indeed I was more pleased than public school class with 25-28 kids. Can we have more flexibility?
user avatar
Jamie Kiffel-Alcheh November 2, 2019 at 9:32 pm
“Keen-eyed readers will note that the research referenced above showed a benefit to much, much smaller classes of 18 students or less.”
That is not actually what it says above. It says 18 or fewer students per teacher. If a classroom has more than one teacher in it, does that not keep the ratio?
user avatar
Janvi Singh January 31, 2021 at 10:49 pm
It would, indeed, keep the ratio, however, it's uncommon to find two teachers in one class unless one is an assistant who is training to be a teacher. Schools are already short-staffed and under-financed, so it's highly unlikely to see that in the future unless major budget plants are to be implemented.
user avatar
Carol Kocivar January 14, 2018 at 9:18 am
New study on class size in California:
Its introduction enticed more families who would have sent their children to private school to enroll in public school. " Their presence resulted in higher average test scores, but also helped improve their classmates’ performance as well, the authors said."

Article in:
The 74
user avatar
Irma Aldana May 31, 2017 at 7:14 pm
While class size is important and significantly impacts student achievement; it is also important the composition of classrooms. There are some districts that groups students according to their English Language Proficiency. Students with most needs have the same number of students with less Language need and those who are English proficient.
How does this make sense?
user avatar
Carol Kocivar June 22, 2016 at 11:32 am
A bit more research on class size...
A June 2016 policy brief from the National Education Policy Center takes another look at the research and finds....
"Despite claims to the contrary by some policymakers, Mathis concludes that reduction in class sizes may prove the most cost-effective school improvement policy overall. In Mathis’ view, money saved today by increasing class sizes will likely result in additional substantial social and educational costs in the future."
Dr. Mathis is Managing Director of the National Education Policy Center.
user avatar
francisco molina August 13, 2019 at 3:17 am
I have a question: between 18 and 24 students grades K-3 How much cost to have a helper? or When a helper is really necessary and less expensive?
user avatar
Albert Stroberg May 1, 2016 at 7:12 pm
I looked at my 4th grade class photo (California)- 28 kids and one teacher. How are kids now so needy?
user avatar
asoltero March 2, 2016 at 2:13 pm
Class sizes especially in the primary grades should be kept to no more than (20). Larger classes are not conducive to a highly optimal learning in academic subject areas. Smaller class sizes afford the teacher the time and energy to work more effectively within the class in smaller group settings. Studies have shown that smaller class sizes score higher on tests, receive better grades and exhibit better attendance. Reducing class sizes in the early grades improves the achievement gap by up to 38%. Students display less disruptive behavior in classes and teachers spend less time on discipline having more time for instruction. Teachers in smaller classes can diagnose and track student learning and differentiate instruction in order to meet students needs. In smaller classes students spend less time off task or not focusing on the task at hand and have greater access to technology.
user avatar
iemailjillian February 29, 2016 at 5:39 pm
Smaller class sizes are effective because more time can be spent on each person when they need more time.
user avatar
Angelica Manriquez February 29, 2016 at 3:53 pm
25 students for a 1 teacher and a 1 helper woud be ok. Not all for 1 teacher
user avatar
Will Kimbley February 5, 2016 at 12:24 pm
While I completely agree that smaller class size has the potential to increase student achievement, the research shows in practice it actually has a very small effect size. John Hattie's research doing a meta-data analysis of over 800 studies covering some 80 million students shows that reduced class size has only a 0.21 effect size on student achievement which is 107 out of his list of 138 studied interventions in education.
The reason is the research shows that by and large teachers do not teach any differently with a smaller class size than with a larger class. If a teacher does not take advantage of the smaller class size to change the way they teach, it is not going to have much effect.
user avatar
KimS September 15, 2015 at 10:27 am
The issue I'm seeing with the smaller class size incentives is that districts are creating an increasing number of combination or multi-generational classes, with a mix of grade levels in one class. But nobody seems to be tracking these figures.
When a school designs this as an integral part of its pedagogy, that works. But when it is forced on schools for logistical reasons of budget, the kids and teachers suffer. My kids go to an IB school that's designed as an age-appropriate, sequentially-building program. Combo classes are causing parental worry and a lot of time and effort for the teachers in both classroom management and curriculum re-designs.
I don't think this is what the LCFF lower class size mandate intended to do, and nobody seems to be tracking whether the class sizes are combos or not. It's a huge loophole in the law.
user avatar
Tara Massengill April 28, 2015 at 2:13 pm
When I was in 5th grade (I graduated high school in 1999), there were 32 kids in my class. My teacher had no problems teaching us, or keeping us on task. My daughter is in 5th grade this year, and her class has the same number of students. According to my daughter, her teacher is constantly having problems keeping the class on task. I've spoken with other parents whose children are in the class, and they say their children have said the same thing. Is it a sign of the times, a sign of the State of California's education system being that much different from the education system in the State of Tennessee, of is it a sign of the teacher being ill-prepared in general?
user avatar
aimeef23 April 27, 2015 at 4:08 pm
Class size is definitely a hot topic. Some people and research states small classrooms are better and kids thrive as opposed to a larger class size. I think there is a point in which both a small and large class are harmful. There should be enough kids in a classroom to have meaningful discussions on topics. You need opinions and kids need to feel like they can have open discussions. When there are too many students many kids are lost and their voices are not heard.
user avatar
cnuptac March 22, 2015 at 2:55 pm
My husband teaches high school and in one math class he has 55 kids there are no limits for high school and no parent helpers. It's wrong he can't get to every child to help them stay on track during his paid hours so he goes to school a hour and a half early for helping kids if they want it for free and some do come but the kids that are the most behind don't even try and get the extra help Heidi
user avatar
Mamabear March 19, 2015 at 11:37 pm
My daughter has a fabulous second grade teacher, but the larger class size (27) does make her job more difficult. I assist in the classroom 2x per month and notice a difference (for the better) when someone is absent.
user avatar
Brandi Galasso February 22, 2015 at 7:48 pm
Class size matters especially when those classes are not being given the supplies or tools needed to accommodate teaching a larger size class. It's not fair all the money schools are lacking can be found in the paychecks of district employees. Instead of hiring more district employees, put a teacher aide in every classroom. It's another adult it helps immensely and also is a witness in case any thing unprofessional in classroom happens.
user avatar
David B. Cohen April 7, 2011 at 11:00 pm
First, I have to admit I haven't read class size studies. From what I've heard, those finding class size doesn't matter much have not been based on major differences. From an anecdotal perspective, I'll go along with the idea that 10% doesn't matter in my high school English classes. If my class of 30 goes to 27 or 30, it's a blip. Unfortunately, people are using the study conclusions and ignoring the numbers, arguing that class size doesn't matter, period, although the changes I'm hearing about in some California classes are more on the order of 30, 40, 50% in some cases, if we compare across a couple of years. Those incremental gains don't look as bad. We'll just go from 21 to 24. Okay, but the budget is bad - you can go from 24 to 28, can't you? Well, now we just grew class size by 33%. Any studies to say that won't matter? I'll tell you anecdotally that it certainly matters. For high school teachers, you also have to keep in mind the total student load. The NCTE guidelines on this topic suggest that in order to provide quality instruction in the full spectrum of English Language Arts, a teacher's student load should be 80. In California, full time secondary-level English teachers routinely have 150-180 students.

I find it curious that you offer words of caution about unintended consequences for those who want to reduce class sizes, but express no caveats about the opposite argument. I find it troubling that you pass along Bill Gates opinions on education so uncritically despite his lack of credentials in the field and his increasingly obvious agenda in edreform, which many of us in the classroom find increasingly alienating and even hostile.
user avatar
Steven N June 23, 2014 at 5:40 pm
K- 3 issues only: Certainly Mr. Gates is not a research expert in this field. Micro-economists using rather substantial large data sets show the K-3, economically disadvantaged student impact is both statistically significant (learning months per year) and highly dependent on implementation! California's - everybody-all-at-once was a disaster because it widely distorted the market for good K-3 teachers. Now this method becomes a real option for 'high concentration' LCFF districts that want to use a good portion of the 20%-50% of per pupil Supplementary $ to use this method. Outcomes? Depends on implementation and highly effective teachers!
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