I'm at a total loss here......do you not want your parents to know because they don't want you to have one??? And furthermore, how exactly are you gonna keep something like that hidden?......seems to me like your parents should be fully involved with this.....
Wow! The expense for this will be enormous! I have no idea how you are going to be able to do this on your own. You sound gutsy. See if your couch can help you get some kind of benefit going. Go to the newspaper. Or maybe just start it with an Article in your school newspaper. Good luck
As you are well aware, prostheses are very expensive. A specialized prosthesis is even more expensive and difficult to maintain. It sounds more of a "be thankful for what you do have because we cannot afford it" type of situation than trying to hold you back.
I think you are going to have to manage with your current leg. Go have fun and be part of the team as best you can.