In our church, the parents pay for some of the extra-curriculars - generally the off campus ones. If there is a hardship, the church has a fund, but it's not openly advertised so that it's not abused. I see nothing wrong with this set-up. The church spends plenty out of the general budget on the student ministry for all it's on-campus stuff, which includes some big events.
For big things, like the bi-annual international mission trip, the church does special fundraisers. Those trips cost in the 10s of thousands, because we usually have roughly 75 kids going plus chaperones, plus all the supplies needed for housing, food, whatever activities we're doing there (ie, building things), etc. For some trips, the fundraising only covers so much, and parents are responsible for the difference. The kids also have other requirements to earn the privilege of going (bible and book reading and reports, journaling, scripture memorization, working the fundraising events, evangelism, etc.). The one this summer however, the fundraising was able to cover the cost of everyone going with no out of pocket expense.