Doesn't the teacher have a website where assignments are displayed? If not, can you ask her to keep parents up-to-date with regular email blasts? I send home weekly updates to my parents on paper, by email, and I post them on my classroom website. Any 8-year-old, even one without a disability, is going to lose papers once in a while. The teacher needs to cover all the bases. I would politely ask her to do this -- even just an occasional email so parents know about assignments would help -- and maybe mention to the principal how helpful it would be if teachers at the school kept websites.
That being said, if you have a child with a learning disability you're going to have to stay on top of things, whether or not his teachers have good communication skills. Email the teacher or send in notes a few times a week to ask if there are any assignment due dates or field trips coming up. Your son is not going to be able to navigate school without your help. It can't all be the teacher's responsibility.
