A team needs rewards yes but not as suggested.
Teens are a difficult age because they don’t want to stand seperate from their friends and peers because of mockery etc… yep even in a church school mockery etc can still be a big issue?
Actually, does the school have a school council?
If so, why not take your question there and ask the school council for help in building up a Altar Serving Team. Ask them what would get them interested etc. What kind of rewards etc would get them there. Naturally don’t promise anything in the way of rewards but you can find out what interests them.
If you haven’t a school Council then you can ask the headteacher if they will do an assembly focusing on Altar Serving, giving a date time to hold a smaller introductory meeting for anyone interested from the assembly. You may get no one. You may just get one. But if you are short then you are not loosing anything by getting no one.
It may be that like adults, children are waiting to be invited. Not that they are children

But in church some are invited or its the parents pushing them forward. That doesn’t happen in school. But if you could get to know a few more and invite them. Preferably those not already serving in church mainly to allow others a chance to ‘shine’ as such… The ones who may not be doing so well academically, could be asked to serve. Not that you want to make that an issue. But help them feel good about something they can do. Then form them into a team and do some team stuff, eg macdonnalds etc for after school burger or something. But not to make an issue of their grades but to encourage them into feeling good about stuff.
The next trouble maker sent to the head - the headteacher makes them into a server etc, actually rewarding them could enforce positive behaviour as they become wanted rather than rejected…
a few ideas for you