Dr Lesgold Finds That Students in Private Schools Perform Better

Dr. Lesgold finds that students in private schools perform better on achievement tests than do students in public schools. Which conclusion can Dr. Lesgold fairly draw?

A) The difference is probably due to differences in family income.
B) The difference is probably due to the fact that private schools have smaller classes.
C) The difference is probably due to the fact that private schools are more likely to "teach to the test."
D) Students' achievement test scores can be predicted to some extent by the kind of school they attend.