To OP. DS was acclerated for math but the school had their math schedules aligned so everyone across grades did math at the same time. Really it's not rocket science, but most schools can't seem to figure this out. In your shoes I would probably tell the teachers to send home whatever he misses that is important with a note as to what he should do (get him a planner with space to write for each subject and tell your DS to have it at every class).