How do i convince my parents to give me money for me go to hershey park with my school chior.?

Offer to pay HALF. $20 more would NOT be hard to come up with if you get out and go do some chores for people. It's spring. Ask a few friends or neighbors for odd jobs. Explain why you want them. Do a GOOD job and you might even earn a little bit more. You should be able to get $20 in just an hour or two. Don't complain ... WORK. Frankly, I'm with your parents on this one -- at least to a point.