I do not mean to incite your anger, only to speak what I discern as Truth.
His teachers - whatever their intentions - are complicit in his slavery. His consent is not being respected in that environment. This is a fact. They act as authorities over him, implicitly threatening him with psychological punishment on a daily basis, and the entire institution of which they are an agent is anti-human; permitting no individuality, but holding all to an arbitrary and universal standard of behavior and education - one to which the student has no natural obligation.
If it is a public school, or if their school receives any government financing, these teachers also benefit from blood money garnered through coercive taxation. The fact that they may be nice or that they "mean well" is irrelevant to their moral standing. The road to hell is said to be paved thusly.
If this does not accurately reflect your views, I would not suggest you speak this to him, but how can you see this any other way? I do not believe he should make them his enemy, but they have certainly made themselves his enemy (in practice if not in intent). There is no virtue in hiding or obfuscating the truth in order to spare his feelings, or in attempting to cunningly direct his growth by a deceptive presentation of the facts.
There is nothing to talk about with teachers until they discontinue their association with government-imposed, compulsory educational standards. Until that time, they are agents of fascism and complicit with evil.
He is being victimized, as an ongoing condition, and purposefully so by those who make these decisions on the highest level. How you cope with that fact is up to you, and you may do so without anger (although anger is not an invalid emotion in the face of injustice). You may certainly council him in sound coping practices, but the truth stands and should be acknowledged, no matter how uncomfortable that may be.
Likewise, his petitioning those who act in an inherently immoral capacity - those in government - is ill-advised under any circumstances. They have no rightful authority, and to ask them for anything is only to support the lie that they do. Go petition the offenders directly, asking them to stop polluting.
Do not ask for a man to make "law", as if such a thing were even possible. God (or whatever the source of the universe) has the unique power to make valid Law, not man, and man's law is either in accord with it and thus redundant and unnecessary, or out of accord with it and thus illegitimate.
RE: CIVIL DISOBEDIENCE - FRIDAYS FOR FUTURE