It’s “degrading” because the teachers were collecting money for use in their classrooms. If it was just someone doing it who happened to be a teacher, and they could do whatever they wanted with the money, then whatever, no one would care. Having teachers do it for the purpose of school supplies? It would be like asking medical professionals to grab money for bandages, or firefighters doing it for flashlights, etc.
Would I do this for money for myself? Sure, maybe. Would I do this for supplies for work? No. My employer should provide that. Putting me in the place where I feel like I need to do this to better my place of employment… that’s the problem.