This.
It's not just sips of alcohol though, he regularly takes it and drinks with his friends and then lies even though it’s obvious. The same with the vapes.
So its not just your DS that's doing it.. but all his friends at school. Are they about to be expelled? Or just him. I'd be looking into that.
He's been at that school since he was 7 and they haven't been able to sort him out?
Is there a chance that they are one of those private schools that believes in "weeding out" kids who look like they may not perform well in forthcoming exams, there by denting the schools exam record which they rely on for recruitment?
You are angry, and that is understandable and you are seeking ways to punish him for his behaviour.. by doing something that punishes the whole family. I'm with your DH on this one. Supposing you did that. How would that actually help the situation. as many have said having to leave a school he's been at since he was 7 is already consequences and punishment.
You need to find out what's causing this, until you do, you can't improve the situation. Maybe some on here will have some ideas of people/organisations you can get individual RL advice on how to help him. He needs your help, he's dug himself into a great big pit that he can't get out of on his own. He needs to be able to trust you enough to confide in you and not just get a telling off. He needs an advocate. Does he have a good relationship with his older brothers?
Some kids just need more supervision with homework, getting into routines, going back to square one with learning to organise themself, or they cannot understand why they are always on the back foot
. Often its no good telling them to do it, you have to kickstart it, get them into a routine, literally sit at the homework table with them ( read a book or something) and keep them company as they get it done. Its surprising how much they open up and tell you more about school if you do. And once they get into a routine you can ease up and let them do more on their own.
The carrot, not the stick.. It can be incredibly frustrating when you want to criticise a poor effort, but you need to instead show them how to improve it. It may take a bit of time, but it does help get them out of the homework hole they've dug. Then they are less likely to aways be in the bad books at school, having forgotten something or not completed homework or brought in the right books. Often that's all it takes for them to feel the whole thing is hopeless. If that is one of the issues. It really can be fixed.
If they feel that everything is boring work boring lectures about how they haven't done well in this or that, and they feel like they will never succeed in anything , they can just give up. So a balance helps. eg school holidays. A day or two of something they like, a day or two of work... No point setting unachievable targets. Their brain is saying this is not school time. Adult brains are worrying they need to catch up.
Don't compare him to his brothers. Completely different generation. Completely different world growing up.
University isn't at all tempting to a 14 year old. If he's adamant that he doesn't want to go, it sounds like he's rebelling against an idea thats been suggested to him quite a lot. "If you don't do that you won't get into uni." That seems decades away to him. Not sure which year he's in but maybe worth focussing more on the near future. It's also worth saying to him. Get through your GCSEs then you can drop the subjects you hate, and pick fewer ones that you actually like.
If there are particular subjects they really struggle in, it seems counter intuitive if they are at private school already, but maybe a one to one tutor would help them fill in the gaps and catch up. If it got them back on top of a subject, it would be worth it, to feel that he might succeed in something.
What other things interest him. Clubs. Sports, etc. The more activitiies he has the less chance he has to get bored and find more troublesome things to do.
So I think you should all go on the holiday. Change of scene. But if he's in disgrace throughout.. its not going to move things forward, or improve communications. Instead (and I know it will be frustrating) try taking him out, buy him a big ice cream and ask him about his favourite band/game/sport or film... and talk about something that isn't school, or what he did wrong. Adult to almost adult. I think that is the way to get him talking and for him to feel heard. Im not saying kid gloves and reward him, but it's about trying a different approach as he's growing older. Then you can move on to getting him to suggest solutions and what he needs to change. I know its an uphill task but Wishing you the very best of luck x