Probably no argument is more important to pro-voucher proponents than the claim that the public schools are in a state of crisis that requires immediate solution. Remarkably, there is very little evidence that supports this conclusion. In fact, much of the evidence cited by critics of the public schools proves exactly the opposite: the public schools are doing surprisingly well despite the hostile political climate of the past two decades. Voucher proponents, for example, frequently claim that the decline in aggregate SAT scores since the 1960s indicates that the schools are doing less well than before. In fact, the evidence points in the opposite direction.
Since the early 1960s the composition of people taking the SAT has changed dramatically. In particular, many more poor students, minority students, and students from the bottom three-fifths of their class are taking the SAT than in the past. Historically, students in these categories have scored much less well on the SAT than white middle-class or white upper-class children. Accordingly, aggregate SAT scores declined between 1960 and 1980. This fact is neither disturbing or surprising; that's exactly what's supposed to happen when the pool of students taking the SAT contains an increasingly large number of less-adept students (See David Berliner and Bruce Biddle, _The Manufactured Crisis_, pp. 14-23 for a good treatment of SAT data).
But note: since the early 1970s, it has become possible to disaggregate the SAT data, i.e., separate the scores by ethnicity, socio-economic status, and class rank. Curiously, when the data are disaggregated, it becomes apparent that virtually every subcategory of students taking the SAT has improved its score. Gains since the 1970s have been particularly dramatic for the poor and minorities. White students have done very slightly less well, but this probably reflects the greater number of white students from the bottom three-fifths of their class taking the test (Berliner and Biddle, p. 20-23). Hence, we have the paradox of everybody doing better on the SAT, but the aggregate score still going down because the composition of the student pool taking the SAT has changed. In mathematics this is known as "Simpson's paradox" (see the Sandia National Laboratories' report, "Perspectives on Education in America," Journal of Educational Research, May/June, 1993, p. 272).
If critics of the public schools are consistent, they should conclude from this evidence that the public schools are getting better. This is not, however, a conclusion that we have seen critics draw. Sadly, our experience of the usenet suggests that declining SAT scores are routinely cited as proof that the public schools are in decline. The evidence suggests just the opposite. In fact, when Sandia National Laboratories adjusted the 1990 SAT results to reflect the composition of the 1975 SAT takers, they concluded that the aggregate SAT score had improved by over 30 points (see "Perspectives on Education in America," Journal of Educational Research, May/June, 1993, p. 270)
There are some additional points to note as well:
The charge that standardized tests supports a recent decline in the effectiveness of the public schools, in other words, rests on an a misinterpretation of data from one type of test which, when interpreted accurately, suggests that the public schools are improving, and ignoring data from other tests which suggest that the public schools are performing better than in the past.