I think we paid $15 or $20 for the trip. I was a chaperone. When the teacher booked, she ordered the pizza party and was told that it would be enough for each child to have lunch (YCA would provide the juice). Teacher confirmed that the children were 6-8 (Montessori classroom), YCA assured teacher that in their experience it was a good lunch. Kids made their pizzas, they were about the size of a bread and butter plate

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All of them, even the eat-like-a-bird kids were looking for more food. We had always planned to take the class to the park after YCA - we still did that, but I went to Little Ceasar's to buy 4 of their hot-n-ready pizzas - we had a picnic in the park. So, for an 11 year-old, I definitely wouldn't recommend it.
We had themed DDs party as a cooking party (prior to YCA trip), and while it was a bit wild, it was a ton of fun and something I would definitely recommend. We made grilled pizzas (I made the dough ahead of time, but the kids shaped it and added sauce/toppings). The kids also made chocolate crinkle cookies that I put in nice cellophane bags and attached two recipe cards - one for pizza and one for the cookies. DD was 7, so we also did the decorate an apron craft, but for an older boy, you could have them make the dough (kneading is a lot of work, but can be fun), add a salad or veggie tray to the mix, or have them make something else age appropriate. We have the Cooking with Kids book from Williams Sonoma and the Rachael Ray 30-minute meals for kids - both have great ideas!
The party at home probably cost a bit less than the YCA party (not much, but a bit), but I think the kids had more fun, and definitely more to eat. Frankly, I would find it embarrassing to send a kid home hungry the way YCA did.