This is what you do:
1. You check Edline at least once a week yourself.
2. When you notice something untoward, talk to your kid.
3. If the issue can only be resolved by a teacher, he has to write an email on the spot (not one month later) to this teacher asking why he got an E or whatever his question is.
4. The teacher should respond within the next few days, and if he or she doesn't, then *you* send an email to the teacher and cc to the grade coordinator, including your son's message in the email.
Our middle school teachers have been extraordinarily responsive to my son's emails about grading mistakes, so I have not needed to intervene. But my friends have complained about their kids' middle school teachers who are not responsive. Things have to be settled quickly when it comes to grades, otherwise the work can be lost, people won't remember, and there will be no evidence left.