What should we do if my son is charged with felony for a pocket knife and some zip lock bags after jumping at a bully?

My son had been bullied for most of the school year and administration had done nothing to stop the bullying. My husband and I have made numerous complaints. Just prior to the end of the school year, my son was jumped by the bully and injured. The very next day, my son's car was searched because the girlfriend of the bully and two of her friends made false statements that my son had a gun in his car. No gun was found, but a pocket knife and some small zip lock bags that my son and husband use for fishing tackle and fishing weights were found. These were completely empty. My son was expelled and remanded to attend interventional school before he could return to his main school. The expulsion hearing charged him with possessing a weapon and contraband. Neither of these two items are criminal offenses according to local police who were the ones who actually searched his car. We have appealed the decision to the superintendent and now school board. The assistant superintendent tells us the pocket knife in the locked car and the bags are felony charges. What should we do? Our son does not want to go to the high school because, frankly, he has no faith in the school. As he has never been in trouble before, we don't want him going to the interventional school because we don't feel that is warranted. Until this is resolved, he cannot attend sporting events, prom, or even walk with his class when he is ready to graduate. We are in South Carolina. Thanks in advance for any assistance.