Average public school, what really bothers me is why I should in

Average public school, what really bothers me is why I should involve so deeply for what my son learns at school. Teaching is school responsiblity not parents. Every night, I have to sign my name to verify which book he read and how long he read and what & how long he practise online math. Every week I have to review all his exams, sign and put comments on it. Every other days I get email from his teachers to remind me what my son need to do next day... Everything online, teachers and students progress. School wants parents involved to supervise kids study, but I really don't want to. I have a full-time job. :(