The US Department of Education’s guide detailing How Faith Communities Can Support the Public School (full pdf here).
The Boston Public Schools Pamphlet for working with faith based institutions (here).
A guide put out by the ACLU further clarifying the laws has been helpful.
Guidelines set by the Center for Public Education are also very good.
Various article from First Amendment Center helping to define the law properly are also very valuable (a nice overview can be found here, a nice teacher’s guide here). The First Amendment Center is a group of lawyers and scholars on constitutional law. They offer a summary of the guidelines for cooperative arrangement with faith institutions based upon the department of education’s standard.