The school board or the counselor at your local high school (or a number of Internet sources) will be able to tell you what courses are required for high school graduation in your state. If you aren't sure whether a certain course has been properly completed or not, Google
for syllabuses and compare them with the work your son has done. After you mark off each core course as completed, sign your son up for a nationally standardized test (AP, CLEP, DANTES) covering that subject. Whatever college your son applies to will accept the test scores as evidence of completion.
Short version: No, I don't know of a reliable transcript service in your state (NJ). All the transcript service would do, though, is verify the courses that have already been completed, and you can do that even better through standardized testing.