States and territories can decide for themselves whether to take part in state-by-state comparisons.
The agency said the study results should not be used to make state-by-state or city-by-city comparisons.
Congress is now considering legislation that would permit state-by-state comparisons of student achievement for the first time.
He made a state-by-state comparison of 1993 public records listing obesity and religious membership, and used 1990 data from a national survey of 3,617 adults.
The Federal agency has produced surveys of students' performance for 20 years, but this was the first time it released state-by-state comparisons.
And instead of drawing comparisons among four artificially defined regions, it would offer state-by-state comparisons of the test results.
Congress recently authorized increasing the number of samples, for the first state-by-state comparisons of student achievement.
And as with per-pupil expenditures, state-by-state comparisons yield no telling correlations.
New York's drop in crime stands up a lot better in state-by-state comparisons.
One important area that the center said it had difficulty measuring was learning, because of the absence of data that would allow state-by-state comparisons.
