You are 100% doing the right thing not letting him go.
In agreement with a pp, it’s more about safety than punishment. As a teacher who has done countless day trips but never a residential, it is sooooo stressful making sure all children are safe at all ones and an overwhelming responsibility. If children can’t demonstrate consistently in school that they can conform and follow instructions, you cannot be confident that they will on a trip...risks are countless, getting lost, injuring themselves and others or worse. It DOES ruin the experience for everyone else as well! In high school I went on a trip to Austria. Two girls managed to wander off and somehow accepted drinks from men and ended up halucinating and fitting infront of us all, it was horrendous, they were ok in the end but had to go to hospital and we all were traumatised. I can’t even imagine how awful it must have been for the teachers! Granted, we were older than your son, 15/16, but not following rules has potential for disaster.
As an aside, and I mean this in the nicest possible way, your opening post where you describe the behaviour as ‘general silliness’ is part of the problem. You are minimising your sons behaviour, he too will get this message which won’t help communicating to him the seriousness of it.
Honestly, I’ve rarely come across a parent who actually accepts their child’s behaviour is bad without excusing it in some way, often blaming influence of peers.
Please don’t do that, please explain to your son that it is HIS behaviour, no one else’s, and HE is choosing not to be respectful and follow school rules.
As an aside, I ALWAYS look for reasons for children’s behaviour, there is always a reason for bad behaviour HOWEVER, this does not EXCUSE the behaviour, rather EXPLAIN it. Consequences are still needed no matter what the need. Once the reasons are understood, work can be done to try to unpick it and to improve it.
However, whatever the reason, it is NEVER resolved by parents not addressing the behaviour or not communicating to the child that their behaviour is wrong. Consistency of approach between school and home is always a first step, letting ‘teachers deal with it’ as a pp suggested, is never helpful!