Can I be forced to give up my photo copyrights to be a member of a group?

That "rule" is going to prove to be a tremendous exercise in futility and waste of (their) time when someone decides to contest it in a court of law, using the First Amendment as cause. NO ONE can force you to surrender/hand over YOUR artistic property also known as YOUR copyright, yours the micro-second you press the shutter release button, regardless of who the camera owner is! NOT EVEN an official government law enforcement personnel can demand or order you to surrender your images or to erase said images in YOUR camera or your memory and they cannot legally confiscate it without a court order!

Of course, the school will CLAIM that it's to protect the privacy and safety of the youths, and that is indeed understandable but if the other youths and their parents KNOW you and/or are willing to sign a release then it does change matters. You must understand that parents and school teachers/staff and administration are taking precautions against POSSIBLE child predators or abductors (whatever else) and in today's world, that an honest concern for parents. Meet with the teachers and coach, introduce yourself and offer to give them a copy of the images for their bulletin boards, to share with the school youths, team members and parents. Be nice; you can't just (Humphrey) Bogart your way in there!

Personally, I would also like someone contest the practice where some concert venues prohibit photographing performers concert goers/audience; I believe that, like malls and amusement parks, are NOT private once they open and operate for the PUBLIC that enters onto their property. In other words, once a private property allows, invites and welcomes the public to use its "property" (for which they already have an incentive, monetary reward) it becomes PUBLIC by practice for all intent and purposes of the law. This practice at concert venues is nothing more than slick operators abusing, infringing and violating legal, civil and constitutional rights, freedoms and liberties of individuals. It cries out for a nice, old fashioned court battle but who will champion the cause of individual constitutional, civil and legal rights, freedoms and liberties against opportunistic sly, slick and greedy concert venue owners/operators and their gang of shyster attorneys?

It's a free country. You can sign the agreement or refuse. When they ask why, you can explain to them that you want $25,000 per photo pr video, if they're going to use it in any commercial way, for each use.

Yes, they can do that. They can also stop your from taking pictures during practices and performances anytime they want.

What copyright? Did you publish them? You are taking photos of this organization's events. I believe they have that right. But wouldn't you be happy if they wanted to use one of your photos in an ad or brochure or something?

No