Hi, just wanted to add a comment that might go against the majority but hope it helps…
My (now 17 year old) son started a similar role when he was 15. He’s a football lad and it was coaching 5/6 year olds for the local community on a weekend.
The role is normally undertaken by students doing DofE and (unlike your son) it was explained that the first 12 weeks are voluntary and then the lead coach picks who they want to stay on / pay.
My son wasn’t going DofE but wanted to get a head start on his CV.
2 years later he still does it and not only gets paid but also got “promoted” to supervisor / pay rise since. He got DBS check and also has done FA qualifications.
He now also works at McD’s while doing his A-Levels.
My point is, it looks great on his CV, and the “initial voluntary period” is quite a common thing with community run clubs. They sift out those who aren’t committed. It does genuinely often lead to paid employment.
So honestly I would chalk it up to a miscommunication rather than a big plot to take advantage of children, and I would be very hesitant to rock the boat.
Yes it’s disappointing for your son that he’s not getting paid atm, but they are also providing him with valuable work experience and an excellent thing for his CV (so many things he can write on it about that role)
Sometimes the actual CV enhancement / work experience is more valuable in the long term.
I’d recommend he sticks with it, and he can look elsewhere for paid work but keep this going for his CV for now.