Do Public and Private Schools Compare?

The National Center for Education Statistics released a study Friday comparing private and public schools and factoring for socio-economic differences between the two populations. The study measured fourth grade and eighth grade reading and math achievement using the National Assessment of Educational Progress, which has been testing children for more than thirty years to provide information to policy makers. In summary, the report concludes that after factoring for population differences, there is little difference in achievement for students in public vs. private education settings.

The study is now being referenced widely in discussions of education reform, particularly in the debate over school vouchers and the overall effectiveness of charter and private schools. To its credit, the study cautions against drawing specific conclusions about the two populations due to the heterogenous populations of the schools, sample size, the fact that this is not a randomized experiment and that a student’s prior achievement is not available to determine progress. Let’s take a closer look at this study, to see what conclusions can be made.

The Scores

After adjusting for socioeconomic factors, the test showed almost no difference between private and public school achievement in fourth grade reading. Eighth grade private school students, however, had a statistically significant advantage over public schooled peers (7.3 points). In math, fourth grade public schooled students outscored their private schooled peers (4.3 points). The difference for eighth graders is not statistically significant.

Without knowing more about the populations and the individual students, it is difficult to make any conclusive interpretations as to what this means. Does it mean, as many are claiming, that the public school is performing as well, and in some cases better, as the private schools? Or does it mean that the longer you spend in the public school setting, the greater the effect it has on your overall performance, leading to a general decline in scores? Combined with research done on vouchers, it would seem that the latter might be the case. Interesting in that it tracks the same children over time is this study of vouchers:

There have been eight random-assignment studies of school voucher programs, and in seven of them, the benefits for voucher recipients were statistically significant. In Milwaukee, for example, a study I conducted with two researchers from Harvard found that students awarded vouchers to attend private schools outperformed a matched control group of students in Milwaukee public schools. After four years, the voucher students had reading scores six percentile points above the control group, and standardized math results 11 percentile points higher. All of the students in this study (which is mirrored by other research) were low-income and Hispanic or African American. — Education Myths

The Test

Tom Loveless has pointed out in a paper for the Brookings Institution that the NAEP mathematics test does a poor job of measuring the skills that it is purported to measure. Calculator use is allowed throughout, so it does not measure basic arithmetic ability. More advanced topics such as algebra with fractions, are also all but absent, making it a poor test of these more advanced skills. If there are differences in either of these important areas between the sectors, the NAEP will not pick it up. It is natural for scholars to want to analyze the data they have, but readers should be aware of the shortcomings of those data as a measure of both basic and advanced mathematical ability. — Cato@Liberty

Another factor to consider is the different teaching methodology which exists between public vs. private school. Public schools have long been driven by standardized tests and use them widely as assessment tools. By the fourth grade, the public schooled student has a strong familiarity with this method of assessment. How much of the advantage shown to the public schools in fourth grade could be attributable to the students’ familiarity with the testing format?

Race and Gender

In the summary (page iv), the report notes:

For all four analyses, with student characteristics such as gender and race/ethnicity incorporated in the model, the inclusion of school characteristics (e.g., teacher experience, type of school location, school size) had little impact on the estimate of the average difference between the two types of schools.

With all the emphasis on the physical environment of the school, it is interesting to note that it hardly factors into the equation of test performance. Many people assume that private schools have the advantage in this area, but that is not necessarily the case. They do tend toward smaller class sizes, but in other measures of “quality” classrooms, public schools often have the advantage. Consider the following:

The average public school spends $8,287 per student. The average private school spends $4,689 per student.

Public schools place a higher emphasis on teacher certification. The practice varies among private schools, depending largely on whether the school is accredited.

Public school teachers earn 25% to 100% more than private school teachers.

With increasing pressure on the public schools to perform in the reading and math assessments, more class time is being devoted to these subjects, often to the exclusion of other subjects. One common model provides 180 minutes per day for literacy instruction and 90 minutes for math instruction. That is 4.5 hours of the school day before PE, lunch and other interruptions to the school day, leaving little time for any other subject. Private schools manage to teach literacy and math while also teaching science, history, bible (presumably, at least in parochial schools) as well as art and music.

While private school may not offer a panacea for all of our nation’s education woes, it definitely provides a quality, cost-effective education to students from a variety of backgrounds. Increasing the choices available to students through “school choice” or “voucher” programs helps give real educational opportunities to children who otherwise would be stuck in their district.

One thought on “Do Public and Private Schools Compare?

  • December 14, 2007 at 6:59 pm

    I agree with you Jennifer! After having my 2 older children in public (both dropped out before graduation) and having my two younger children in private–well there is no comparison! One of my younger children started out in public, they put him in title 1 in grades 2 and 3, and he was failing all subjects! When I approached the teacher about holding him back she said “we don’t do that anymore because it is too detrimental to the child”–uhh–isn’t that setting them up for further failure?? I had him tested for private school and they determined that he did not need title 1 for reading(as in public school) but that he needed help with math instead. Today, 3 years later, this child has adjusted very well and even made it to the regional spelling bee! His math scores have increased also and he is right where he is supposed to be for his grade level. And yes, they are tested in this school. Our town does provide extra curricular activities (because the school can not afford them) in the form of sports (year round), art and music. I am very happy with private school and would not consider putting my children back in public. I regret that I did not pull my older children out sooner and put them in private–maybe they would have had a better chance of graduating.

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