If the student expects to be paid anything signficant, then the student should consider what leverage they have over the organization which could simply abandon the whole project.
Isaac, good point there. If Blankrider is still paying attention to this thread, it might do to discuss what actual outcomes are good ones with his/her parents.
For example, if the student asserts his* copyright what will the organization do? What will the broader association of organizations do? Would they consider purchasing the program from the student without the recommendation of the local-based organization? Maybe first he should put the local org on notice that he is the owner of the program, but at the same time signal a willingness to work together with them to further sell/distribute the software. I don't know what's reasonable in terms of rate so of course my ignorant assumption is that a 50-50 split might be a good start.
*(sorry, I'm going to switch to gender male old-school used to be considered neutral since the "her/his" stuff trips me up at this time o'night, forgive me)