## Data First

Brought to you by The Center for Public Education

Home > Data Center > What is our average class size?

## National Data

According to the National Center for Education Statistic’s Digest of Education Statistics 2012, the national average number of students per teacher was 15.5 in 2010.

## Data Source

The National Center for Education Statistics (NCES) calculates the number of students per teacher for the nation as a whole. You can find student per teacher data for specific at the school and district levels at SchoolMatters.

## Summary

NCES calculates the number of students per teacher using the following formula: Total student enrollment divided by professional instructional staff. NCES  publishes the data annually in their Digest of Education Statistics report.

## How to Use the Data

Student-teacher ratios can serve as an estimate of class size, and research has shown that under certain conditions reduced class sizes can boost student achievement. These ratios can also be one measure for judging whether your schools have an adequate supply of teachers.

### How the details were measured

The data is presented as the number of students per teacher. It cannot be broken down by race or poverty level.

### Limitations of the data

The data defines teachers as all professional school staff members who provide instruction to students, so it does not distinguish between non-core subject-matter teachers (like physical education and art) and core subject-matter teachers (like math and English). Moreover, users should not compare schools and districts across the states, because states submit data with differing definitions.

What is the average class size?

The average class size is not the same as a student-teacher ratio. The two measures can produce different results, because some teachers may have non-classroom teaching assignments, such as working in a writing center. In order to get a solid grasp of school and district context, you should examine them both in conjunction with one another.

How is the student-teacher ratio calculated locally?

When comparing local rates to state and national ones, you should be sure to know the exact definition of a teacher used within each approach. Student-teacher ratio data collected by NCES uses a fairly broad definition and includes any professional school staff member who provides instruction to pre-kindergarten, kindergarten, or any non-graded classes. Other states and districts may exclude those who teach pre-kindergarten, adult education classes, or non-core subject-matter classes. When comparing local rates to national ones, you should be sure that you are comparing apples to apples and that the data has the same underlying definition of a teacher.