Take a good look at the age group and size of the shooters you will be getting.
1.Talk to some older shooters at your club or area clubs as many shooters have more than a couple of trap guns such as 1100's(common gun that can be modified and maintained) BT-99s and BT micros(again easily maintained and can have adjustable butt pads installed)
2.THese older shooters for the most part are very receptive and a lot of the time will make you a very good deal or in the case of very generous people will donate.
3.Keep you selections to one or 2 types that way you can keep common parts around and maintain your inventory for longer life through your program.
4.At our club gets a lot of use out of BT 99 micros.
I've worked with the local High School team and also just watched as a range official. I think the Browning BPS (bottom load and ejection) is an awkward gun to load specially for a youth and is just hard for anyone from a distance to observe that the action is open when required. These young shooters need to be reminded occasionally of the safety aspects of handling a loaded or unloaded shotgun.
Plan on figuring in some stock adjustability. Either added or built in at the factory. Both Length of pull and comb height and position.
Also don't forget the lefty.
Have a few and had to set up something different for them. Our right hand ejecting autos just were not practical in that situation.
Also agree on keep it to one type for spare parts and maintenance simplicity.
I wouldn't buy a BT-99 if I could help it just because of the lack of versatility. All the kids down here also shoot at least some 4-H and since they shoot trap, skeet, and sporting clays a BT-99 won't work. I know that in a lot of places there are trap specific clubs, but if at all possible I think I would be trying to snap up any used Browning XTs and Crossover Targets I could find.
The reason I ask is because the guns on my kids team are passed around like a hot potato and an adjustable comb and LOP would be worthless. She is on a rather large team and roughly 20 kids use team guns
I help with a youth team and we have a hodgepodge of semi-reliable 11-87s and hideously bad Stevens 555's. A couple of the kids (including mine) shoot the synthetic Beretta A300. I would love to move all the kids over to those. Softer shooting than the 20 gauges we have, basically bulletproof, and easily adjusted for LOP. Even the 12 year olds have no problem with them.