We had a similar problem. We found that the district and administrators were much more willing to help us out when our equipment was in bad shape when we pointed out how much money they make through the
theatre, they use it for assemblies, school fundraisers and the like. When they realized that if they didn't help out with the money, their projects would be happening in the dark, they got helpful fast. Plus, you mentioned that you have to pay tech students for the productions. Methinks, if they aren't your productions, say if they're for a student council fund raiser, we make the other organization pay the techs. For performing arts functions, we have a letter point system. Essentially, for every mainstage show, kids get 10 points for being on crew. For a band concert, they get 2 or 3. At the end of the year, kids get awards for having high letter points. That may solve your issue with paying techs.