Instead of keeping up with all the missed assignments try using this responsibility report sheet. The teacher can have a student fill this out for homework or classwork that isn't complete as well as providing the reason why it wasn't completed. The teacher can keep this document until they provide the work necessary. It can be used during conferences to show the parent/guardian the amount of missed work and the reasons why.
At the signature line I used a cute math clip art I found, if you would like something else just email me with your ideas and I will send you something designed for you.