My daughter went through the stage of biting as well. We finally figured it out, that she was having trouble with transitioning to different areas of school..i.e..lunch, gym, recess or even the washroom. A teacher went with her and helped her with her transition and it worked so well. They also tried a visual chart with her at school to show her what was next and where she was going, so that she felt more in control of the situation, which also worked great! Good luck!!
You need to take this problem up with the teachers, if they are good special ed teachers , they should be able to come up with a solution. If he doesn't bite at home, then something is getting to him at school. As far as the reading goes, don't push him, let him learn at his own speed. there is way too much pressure being put on the DS child and we are seeing physch problems because of it. I never saw the physch problems in the older kids, now it is showing up because the schools and the parents are trying to "make " their child normal. At home I taught my son reading words by using flash cards, also got some programs for the PC and he learned more. Reading is not a main thing for a DS, teaching independance in living skills is more important. Reading the danger signs is good. Sign we see that tell us what to do. Reading will never be a big thing in the future of your grandson. Daily living skills, behavior, sports, good hygiene, counting is more important, tell time, money ideas, your grandson can grow up to be a fine young man, if just given the chance. A very wise teacher told me one time, to never let a behavior go that would not be accepted as an adult. So the bitting has to stop. Good Luck.