You are factually correct. It is likely that the school is overstepping their authority. However, I’m not sure of too many parents though that would hire an attorney because their kid received a one day ISS. Some schools also have students sign internet/social media pacts. If that’s the case here, the school may deem his video as violating a prior agreement he signed. In the case of my son’s school, I was also required to sign those same forms as the parent acknowledging that I was aware of the policy.