Thanks for all the responses. It's good to know I'm not alone and the advice is much appreciated.

He has an IEP in place, but it will need to be amended to address the teacher signature mandate. All but two teachers (one who used to teach special ed and the other with a sister with dyslexia) have been actively resistant to having to get more involved with keeping him on track. They would like to make it my responsibility, but the disconnect is happening in the class. So that is where it needs to be changed. I think the signature idea is great.

I wish I could say he is distressed or feeling like a failure, and this was driving him to find solutions, but in reality, he's a little surprised I'm concerned. "I'm learning the material, Mom," he says. "Why do they need a bunch of paperwork to prove it?"