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Home > Blogs > Get on the Bus > Archives > 2006 > July > 15
Saturday, July 15, 2006
Are private schools really better?
Here’s a lesson in education statistics and how assumptions may not always add up.
At first blush, the results of the National Assessment of Education Progress — a standardized test given nationally at fourth and eighth grade sometimes called “The Nation’s Report Card” — seem to affirm a commonly-held belief, that private schools produce better academic results than public schools.
Here are there results of public school average test scores compared to private from NAEP:
4th grade reading: Private schools scored 14.7 points higher
4th grade math: Private schools scored 7.8 points higher
8th grade reading: Private schools scored 18.1 points higher
8th grade math: Private schools scored 12.3 percent higher
All those margins are big enough to be statistically significant, the usual standard by which researchers judge one group’s out-performance of another to be reliably believable.
But in a study by the National Center for Education statistics, researchers tried to make the comparison more apples-to-apples by controlling for outside factors that affect test scores, such as gender, ethnicity, disability, English language learner status, school size, location and the composition of the student body. Using a statistics model, they re-ran the comparisons while controlling for those factors.
Here’s what they found:
4th grade reading: No significant difference between public and private schools.
4th grade math: Public schools scored a statistically significant 4.5 points higher.
8th grade reading: Private schools scored a statistically significant 7.3 points higher
8th grade math: No significant difference between public and private schools.
Now, this is just one study using one method, but the results are quite interesting. And they challenge the conventional thinking.
Who the students are, and what kinds of homes they come from, certainly affects the test performance of students in tuition-based private schools. The question is to what degree?
At a minimum, this study suggests the big test gaps in the aggregate scores of public and private may not, by itself, necessarily mean the difference in the quality of education offered is that great.
UPDATE: The New York Times wrote about this study Saturday in a front page story that mentions the study was complete last summer but peer reviewed for a year. The story says teachers’ unions have been asking for the results for months and accurately predicted the study would be released on a Friday afternoon in the summer to gurantee minimal news coverage.
Over at the American Federation of Teachers’ blog, they trumpet the study as good news for public schools and say its results challenge the theory behind vouchers — that kids can get a better education outside of public schools.
Even if the weekend is the down part of the news cycle, there was quick reaction in the blogopshere, including Joanne Jacobs, Joe Williams and Alexander Russo.
There’s an especially good post from EdWize, a blog by the New Your City teacher’s union, that points out this study was commissioned by a Republican Bush appointee.
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