16 year old son being excluded

[LondonBorn]

So I've never ever done anything like this before, but I'm so hurt for my son that I need to or I'm going to burst. My son has done nothing wrong, no bad feelings with any of the friends he has been at school with for 5 years. So last week, a party arranged and he was the only one not invited. Now it turns out they have all booked a prom vehicle and have excluded him from the group, started a group chat without him too !! He has asked them all outright what he's done wrong, and why he's being excluded, and not one of them will answer him. 4 of them have played on PS4 with him today, acting totally normal with him. I am so hurt, I've even cried, sad I know, but he's my boy and he's a clever, bright, liked young man.... Or at least I and he thought he was. Today I've watched him struggle and it's half killed me. He's so hurt. Truly feeling like he's excluded. This is meant to be the summer of his life. Once exams are over next week anyway.
I'm struggling too, as I know if I see these horrid kids at prom I may want to say some choice words to each of them, although I know that won't help the situation.
What can I do ? What if he gets to prom and he's seated with no body who he likes etc. I don't know what advice to give him.
If anyone can help, please do. I've never been lost like this before as a parent.
Thank you for reading

That's so awful. Is there a girl he could go to prom with?

Oh that sounds so awful for him, poor boy. So they were playing with him on ps4 but haven't included him in any of their plans?
Does he really want to go to prom? If he's not fussed I wouldn't bother going. I think prom is vastly overrated, it's a few hours and then it's all over. A lot of the boys at my DD's school are not even going.
What's he doing after Gcses? Is he staying with them or venturing off somewhere new? I think it would be a good idea to cut his losses and move to a new school/college and start afresh with some, hopefully, new, better friends.

I’m sorry you are both going through this, it maybe you are more upset than he is.make sure you don’t project your distress onto him

Thanks for messages.
He has some other people he knows going , but still doesn't answer why they won't have the balls to explain why they are treating him this way. He is staying for A levels, and says he's done nothing wrong so why should he leave the school and teachers he gets on with very well.
I am not talking to him much about it although he knows we are here if he needs us. No chance I will worry him more by my feelings.
Yes he wants to go to prom, he sees it as the end of an era as some people are going off to colleges etc.
I'm sure he will be ok. I truly want to believe that sixth form brings different friendships as you move forward in life. The choices you make from this point are what you want not what you have to do.
I'm calmer today, but yesterday I did not know which way to turn at all.
I am going to be there for my son. That's what I'm meant to do right.

Oh and yes, PS4 with 3 others for almost 3 hours, with loads of laughing going on too !! I don't get it at all

There will be a reason, even if he is not willing to tell you.

Maybe they have plans to take drugs /alcohol and know your ds wouldn't be involved /would report them/wouldn't be happy?
My ds has been with such friends until after a long road he walked away.