But what if you sue to stop the government from doing something to you? What if the remedy you seek is to simply ask the government to stop doing something to you? What if the remedy is to ask the government to stop forcing you to submit your kids to the gross negligence that is the school system?
Your goal could be to simply stop them from spending whatever your dollars per student number is in their demonstrably bad system. Let's say it's $10K per head, so you ask for them to allow you to designate where they spend that $10K. OK, it's a voucher. But, it's a voucher as a remedy in a law suit. The plaintiff is not asking government to spend more or change their system in any way. You just want your kid back, with the money they would have spent on them anyway.
All you're doing is enjoining them from spending the plaintiffs dough at Willies. You're not wagging the dog, just stopping the dog from pooping on your kids.