This idea comes with a big, bold but. The but is that the government need to start funding schools properly. There are quite a number of articles on this list already to demonstrate how this could easily happen. Once schools are given adequate funding to run themselves, there needs to be a ban on voluntary contributions and any donations to the school from commercial entities.
While it’s probably impossible to stop people from fundraising for nice things such as Astroturf pitches or whatever, these events should be for nice things rather than essential things.