I am looking for a dataset that contains the amount of snow that will cause a school to close in the US either by school district, zip code, county or any subdivision smaller than state. I am familiar with this map. However, there is no methodology provided besides a short description.
You may want to read my past question I posted here...
See if that helps yours.
I am not sure for the whole country's school districts. I think that would be too much to perform that kind of work, however, I think maybe NOAA, or probably contact the National Weather Service and query about that . They might help you out where to find it. or contact the each state's Department of Education and ask them about it..
Good Luck on finding it.