We struggle with this dilemma also. It seems the school understands the "SID" label and can accomodate this. I'm not sure they understand or know how to accomodate OEs without the SID label. I agree with the above suggestions for books.
We do sensory stuff here every day and it helps but mostly the cognitive aspect of working one-on-one with the child in sensory-rich environments has worked best for us. I think it would depend on how aware your kiddo is of his sensory overload signs and how well he can cope/ask for a break and how well the school/teacher can make this happen. At 6 that was a lot for our DS to do.
