Here's what's disappeared from U.S. Department of Education website (in addition to Office of Technology info):
(1) An annual school finance survey
(2) Census data that informs the dissemination of funding Congress allocates
(3) Common Core of Data, which provides basic information about K-12 education—such as the number of students enrolled in American districts and schools
(4) NCES Comparable Wage Index (CWIFT)
(5) NCES/EDGE Neighborhood Poverty Index
Here are orgs trying to preserve it:
(1) DataLumos, a crowd-sourced repository maintained by the Inter-University Consortium for Political and Social Research IC (University of Michigan)
(2) Data.Gov Archive at Harvard University
(3) End of Term Web Archive at the Internet Archive, Stanford University, University of North Texas and Webrecorder
(4) PolicyMap
Thank you to National Education Policy Center University of Colorado Boulder for sharing this info and to all of the organizations taking the time to curate and save these valuable data.