NYS Education Department's information & reporting system is a source of education data , but I've also learned of these older resources:
Data, back to the late-1970s, in ascii and SAS transport formats. The State Archives distributes 1967-1982.
CISER also has Statistical Profiles of Public School Districts for 1990-2006 (Lotus, Excel, comma-delimited formats). Recent years can be downloaded from here as "volume 2" of the 655 report.
Needless to say, there are many, many caveats to consider when dealing with these files.