Student:Teacher Ratios

Simon JeynesThe CACE RoundtableLeave a Comment

What is the right number of children in a class? Is this primarily an academic or a financial decision? Does it matter what age the children are? Let’s investigate the different aspects of this important question.


Many Christian schools, with tuition under $12,000 and typically between $5,000 and $8,000, love to talk on their websites about their small class size. The question Boards, Finance Committees and Principals / Heads of School have to answer is what class size makes their school fiscally sustainable. This is strictly a numbers game. It does not relate to academic achievement or student challenge or innumerable other questions that might be brought up. How many children do you have to have to afford opening a class?

We will use the 2017-18 National Center for Education Statistics as the latest broadly available numbers.

Public school average base salary                  $57,950
Private school average base salary                $45,320
Eligibility for the food stamp program based on gross household income

Family of 3 Family of 4 Family of 5 Family of 6
$28,200 $31,536 $36,936 $42,348

The average Christian school teacher salary, based on CSM’s experience, is lower than $45,320 but we will use that number in part because it is a statistically justifiable number and in part because it keeps us out of salary ranges where teachers can’t afford to feed their families.

The following example of two real schools gives us insight into the number of students needed to support this teacher:

 School #1School #2
Number of Students514260
Class Size24.4820.00
Total Expenses4,012,9541,654,282

The number of students is divided by the number of sections (not individual classes) to get a class size necessary to pay for the expenses through a tuition that is a real number. It is interesting that the larger school actually requires a larger number of students per class although the reader should not assume that these budgets are ‘perfect’ or that the school is perfectly ‘efficient’. From this simple exercise, and connecting it to our much wider experience, we can say that a decent budget can be built when the class size is 20 or more. Under 20, and the budget begins to fail in various directions: poor compensation, few or no benefits, underfunded program / mission delivery, not enough people to do the jobs etc. So the financial answer is 20.

Classroom Culture

How large does the class need to be in order to generate sufficient academic discourse that will result in good student outcomes? Research has largely examined the size of class in relationship to the teacher (see next section). But surely common sense says that a class of only two 5th graders lacks a classroom culture that is needed for healthy discourse. There is no obvious answer – maybe we can agree that two is too few but what is the right size? CSM takes the view that a class needs to have 15 or more students in order to:

  • Have an intellectually stimulating conversation
  • Represent a diversity of opinion such that thought and reflection is rich
  • Include gender, income, race in numbers sufficient for there not to be a dominant voice
  • Expand friendship possibilities that can morph and change with the seasons
  • Collect varying interests, hobbies, fads that make for an interesting community

For powerful education beyond the mere accumulation of knowledge requires a rich culture. It is impossible to have that culture when the numbers are too small. The culture answer is 15.


What is a small or a large class and does it matter? The Tennessee STAR study, usually cited as the golden measure of research in this area, considered small classes to be between 15 and 17, with ‘regular’ classes being between 22 and 25. There was somewhat of an effect size for small classes but later research suggested that the effect did not carry through. Ultimately, the strength of the findings is too weak to say that reducing class sizes from in the 20s to the mid/high teens is a good use of resources. The evidence is just too weak.

Reducing class size, of course, makes education vastly more expensive. The trend to smaller class sizes is long-standing as the chart illustrates.

Private schools at one time actually had larger classes than public schools looking at data from the 50s and 60s. However, by the 70s there began to be a war of attrition as to who could get the smallest class ratios. We need to understand that ratios are not class sizes – ratios are calculated using total number of teaching employees, not by counting the numbers of children actually in a class. Nonetheless, the hope of vastly increased academic achievement has not been fulfilled, if test scores are an indication.

Further, according to John Hattie, the advantage of reducing a class from 25 to 15 students has an effect size of only .24. The school loses 10 tuitions, reduces the school’s capacity to run better programs, for example, in fine and performing arts and athletics, and for some but not very much gain. In contrast, there are literally over 100 other interventions without negative income implications that have effect sizes of .4 to 1.57. Examples of these including increasing the efficacy of the faculty culture, motivation/effort, classroom discussion, direct instruction and more.

While it may ‘feel’ better to have a smaller class size, the evidence does not suggest that there are better educational outcomes, and certainly not compared to other options that cost far less. To put it bluntly, the money we lose far outweighs the weak advantages we might gain. The education answer is also 20+.

Public relations

When parents ask for small classes, their idea of what ‘small’ actually means is tied to the context within which they live. In one area of the country, parents were delighted with their Christian school ‘small’ classes of 28 because they were comparing them to the local public school classes of 35 and more. In another area with many independent schools, the assumption was that a small class size was 18 or less because that was common in schools that were charging an average of $24,000 tuition. Certainly, if we tripled our tuition, we could have those class sizes as well irrespective of their educational benefit! Parents, though, don’t really know what they are looking for and attach to small classes as a measure of quality. In our constituencies, so long as their children are being well served, classes can be a variety of sizes. It does appear that the number 3, as in 30 or more, is a toxic number in parent’s minds pretty universally and so the public relations number is less than 30. It will depend on your context, how much less. And remember, we are not competing with those “expensive” schools! Only with schools that have our tuition level.


It is instructive that, if there is any research supporting the idea of small classes i.e classes with less than 20 students, that research applies exclusively to younger grades. Even the most fervent supporters of smaller classes will admit that the number can grow in later grades as students are more able to manage their own learning and take responsibility in ways that younger children cannot.

We can easily accept that class sizes will vary in a three division school, just as the ratios of children to classroom teacher in preschool are also very low. Ratios in classes below kindergarten are subject to completely different regulations requiring an adult be present for every 8-12 children. From Kindergarten up, the class sizes will double. In high school, the presence of electives hopefully from freshman year through senior means that we need the incoming classes to be large. Even so, some classes (think Spanish 4 and 5) will potentially have less than 10 in them!


Based on the current state of research, current realities on the ground, public perception, and financial realities, the following table represents CSM’s opinion:

Before KindergartenDetermined by state regulation (usually 8-12)
K-218 (in reality this is actually 20 since it is unlikely that your school will be able to actually add students in 3rd grade)

Nonetheless, we urge Christian schools to recognize that the size of class and student/teacher ratios are not the most important metric your school has. The effectiveness of mission delivery is ultimately what matters. It is better to have larger classes and therefore have the money to invest in teacher growth, meaningful interventions, staffing for small group work, than to have smaller classes and struggle to make ends meet. We certainly don’t want to dramatically increase tuition in order to have ‘small’ class sizes that have no obvious educational benefit.

What schools should be wary of, and Boards should resist strenuously, is the worst of both worlds – increasing class size and depressing tuition so that stress on teachers increases, public relations is impacted, and there are not sufficient resources. Every additional student is an additional unit of work. We have to invest heavily in our teachers, the primary reason for educational success, and giving them a large number of children without the resources they need is wrong-headed. Have a class size of 20+, and charge the tuition needed to provide exceptional resources for the teacher. That will both improve educational outcomes for each child and motivate more and more families to come to your school.

About Christian School Management (CSM)

Mission: For Jesus; Through Mission; With Students



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CSM is a 501(c)(3) dedicated to healthy, hopeful Christian schools. It works with Christian schools that have an average tuition K-12 under $13,849. 10% of its revenues is tithed into the CSMA Foundation in order to assist Christian leaders and schools with advice/counsel and to fund Christian school research. We charge for consulting based on the tuition level of the individual school to make it affordable for all.

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  • Simon Jeynes

    Simon has been Executive Director of CSM since August 2017. He consults directly with Christian schools that have enrollments of 350 or less and tuitions of $13,849 or less. He provides school-hosted workshops, writes Entheos (the CSM weekly letter), and works to extend God’s kingdom by training and coaching other Christian school leaders to work with CSM. CSM’s mission is For Jesus; Through Mission; With Students. Simon is passionate about reversing the decline in Christian education that has happened during the 21st century. He works to ensure that Christian schools are healthy, happy. CSM is committed to working with schools in a way that leads to independence, not co-dependence. He continues to keynote, speak, and lead workshops at educational conferences including PNAIS, ERB, VAIS, AMS, CASE (2010, 2016 Stellar Speaker), ISAS, NJAIS, ACSI, CAIS, AISNE, NCAIS, ASB Un-Plugged, SAES, FCIS, CSI, Laptop Institute, CBOA, LEA. He worked with ACSI as part of their LeadershipU Program for two years. Simon earned his MA from the University of Oxford (School of Modern History), his BEd (Hons.) from the University of Lethbridge, and his MEd (Educational Leadership) from Concordia University. Mr. Jeynes is married with four children, a dog, cat, and two birds. He is delighted that two of his children are now at university.

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