Our ds class trip is always to disney and its far from what we would refer to as "budget". Even with fund raising we have to split the costs of all chaperones too.
They do the group stuff with Disney along with transportation to a mission project. My one son did a puppet show at give kids the world and this one is going to the orlando mission rescue I think in May.
It helps that the one teacher was the disney teacher of the year twice and is a disney nut too.
I think its about $700 per student. That includes southwest air fare and staying at this time probably carribean beach. They get the vouchers for the food which is counter service usually and I think its about 5 days. They also do 2 sit down meals, usually the character breakfast at AK and then they did whispering canyon last year but a special menu which the teacher called and approved with the restraunt manager ahead of time.
If you want real budget I guess it would be a value resort, counter sevice only, using the magical express,no park hopping etc.