You are also forgetting that most legitimate shops have test sensors, modules, ecm's, etc. If I suspect an ECM, I replace it with a test one in about 15 seconds and see if that fixes it. Meanwhile, someone else has the DVOM and chewed up all their 7/10ths diagnosis time with it. NO point in DVOM testing wiring and everything when you can pop in a sensor, and if that doesn't fix it, you put the old one back in and keep checking. Trust me, you will see when you get out into the real world and see how the parts counter can work for you.
If someone is in an auto class and doesn't know how a TPS works, they either don't belong in an auto (or diesel) program or they haven't gotten to that point yet. If an auto program doesn't teach you how one works? There should be no program....but that is why you ASK questions about the program BEFORE you sign up. Just going to a high price school to save you asking questions about less expensive schools sure sounds like an expensive way to do things.
I have a wyotech diesel grad in my training program with me. Guy knows how to R&R like a sum-bitch, but my times are higher. Point? We both went to school. His was $17,000, mine was $2,000, we're at the same level, but my times are faster. He also did not know how to change parameters with the CAT ET program. In the end? It's not the school, it's you, and how bad you want it. Now...................for the big question.................. How far do YOU want to go, and how important is a 10 year student loan to you that you HAVE to pay regardless of how much you get paid as a novice.....?