Here's my experience, and we do a LOT of school performance/event gigs.
Free to school? We started out charging the school - performing arts class, music class, band, football, grad night, etc. but that didn't work very well. So, we started a "minimum order - direct-to-parents" program with the school group, class or organization (band boosters, for example) distributing order forms, collecting orders and money, either paying us with one check or handing over the checks made out to our company.
Occasionally we've had to kick back a bit, or for major sales of 75 units or more, given a cut to the organizing group or class or school authority. They purchase them outright for a given price and sell them for whatever they can get as a fundraiser or whatever.
I've also had groups purchase my minimum order outright and never hear from them again.
I know copies are made and sold outside any agreement I make with them. I know I'll rarely sell more than 70 percent of the participants due to this. I know even if I purchased a duplicator with copy protection built in, one out of every two people have something that will break the protection and still make and give away, or sell copies.
I DO require a deposit to "hold the date" because if the organization has nothing invested going in there's nothing to keep them from taking a "better deal" perceived or otherwise if one comes along, canceling out on me at the last minute and costing me a gig I might have been able to land elsewhere. So, a deposit to hold the date, refunded, depending on the agreement, if minimums are met, or total sales exceed, etc. They take their cut, if any, deduct the deposit and pay me the difference in one check or whatever.
Exclusivity? It's OK to ask for it, and most of the time the school or group organizers, owner, whatever, will make that announcement - especially if they're riding on the "purchase and resell wagon" and want to make their money. HOWEVER, in the hundreds of school and other events I do a year I've never seen it work. Parents WILL (I paid for their costumes, instruments, dance shoes, lessons, taxes, and admission and by God I'm going to take photos and shoot video if I damn well please) do it anyway.
And the officials DO NOT want to P.O. the parents because that is the constituency they have to depend on for support in many ways. Never antagonize the parents and especially the president of the support group (think band boosters, etc.).
So, ask and get it (the announcement) but don't expect it to carry much weight.
Media Rights? You have the rights to the footage you shot, and the production you created from it. You have all rights for use and marketing or resell or whatever, even repurposing, but be sure you have signed releases for EVERY person appearing or performing. I will not videotape a production without parental release and proof of copyright release to the actual production itself - music, script, performance, etc. - from the organization.
In many instances I can get by with signed parental releases for those ordering because in some performances (dance, for example) I only need to have releases from the acts who want to purchase a copy. If it is an ensemble or group of 6, 8, 10 etc. then peer pressure usually results in all of the parents providing signed releases that are included on my order forms. If an act or acts does not result in signed releases, or releases for ALL, then it simply is not offered or provided until all releases are in my possession.
Primarily these people are going to consider what you produced for them as a "work for hire" whether or not your agreement states otherwise. Good luck enforcing any kind of restrictions or exclusivity unless you're dealing with a professional group, not a school - public or private. They will use the rights they want - and parents will throw up snippets or poorly transferred performances on YouTube with or without your blessing. So will the kids. Good luck fighting that - it's bigger than city hall or the feds. You cannot fight it. It's a losing proposition and will cut way down on your popularity, promotions with other schools/groups, referrals, and renewables.
The more difficult or restrictive you try to make it for the individual, school, group or organization the less business you will attract. I found it simpler to accept whatever minimums I've established that I'm willing to accept and get on with my business life.
I used to sweat and fret over "pirating" illegal distribution, duplication and re-sales, unauthorized uploading, etc. but if you (I) want to do business, accept the loss of sales that comes with it. That IS GOING to happen and if you want to do business in this environment you're going to have to accept that inevitability IMHO.
• Insist upon an agreement
• Get a deposit to hold the date, however you arrange for return or reimbursement, or miniums
• Get releases
• Confirm that the organization has the rights to videotape and distribute copies (for profit, sale or not)
• Establish a minimum number of sales, minimum price and length of time to delivery (I used to think that early delivery was a no-brainer, but soon realized that if I took 4-to-6-weeks to deliver, I got more sales. Early delivery simply cut off my sales because some of those who were slow with the orders then could obtain a copy from a friend)