Clearly you DON'T have a grip or this would never have happened.
I have an almost 18 yr old who is not at school now but who NEVER had a detention, only one of her close friends has ONCE (fragile after a bereavement and another pupil made a cruel comment and the friend swore & shouted at them) and it was a strict school! Not perfect but certainly never treated teachers with disrespect - partly because she KNEW I'd have come down on her like a ton of bricks if she had! One of her best friends in her close friendship group from primary is a boy, I know him and his family well. They too would have not simply "given him a flea in his ear" if he'd behaved like this!
Frankly if that's all you've done that's pathetic. Your son should absolutely be facing consequences at home as well as school for this, let alone you thinking the school or teacher has done anything remotely wrong.
"Also every time I do receive something from school I fully address it with him." If that's the same way as you've "addressed" this then no wonder he's learning nothing. He's not getting anything but a slightly stern chat, that's not enough.
You're doing that classic Aibu thing of
Op Aibu?
vast majority of respondents - yes!
Op - no I'm not! (Metaphorical stamping of feet & sticking fingers in ears going lalala)
Such an attitude and denial will not do your son any favours at all.
"It was just a joke" "banter innit" is the bullshit excuse offensive, thoughtless people come out with to excuse and minimise inappropriate actions/comments.
Snapchat is not solely used for sexual messaging but it IS used for that a lot by teens around this age. You were not there to witness the incident, at this stage you only have your sons word and a brief telephone message for what happened.
Myself and others have REPEATEDLY pointed out damn good reasons (which may even be school policy) why the teacher didn't take your son to one side and speak to him privately. That you don't agree is irrelevant, you aren't the teacher with a career and potentially personal safety on the line.
"I fully believe if this teacher HAD spoken to my son quietly after class he would have fully apologised"
1 it should NEVER have happened in the first place
2 at that age he is well old enough to have quickly realised he was wrong and apologised immediately.
3 even when you DID talk to him about the inappropriate nature of the incident he didn't accept that immediately instead he justified, minimised and denied!
"He is now just feeling confused about what is happening" there's a very simple quick way to make him less "confused" support the school, sanction him, make clear to him it was COMPLETELY unacceptable and inappropriate and you DO NOT expect him to behave this way ever again.
Have you even looked at his SM to check how he's behaving on there? Do you monitor that at all?
Piggywaspushed - he's not taking it seriously I suspect because his mother/parents aren't.
Op genuine question - do you think the type of men who become sexual harassers, assaulters, even rapists are created overnight? Of course not! It starts with them getting away with "minor" behaviour, with their offensive/inappropriate comments and actions going unchallenged.