[alkonaut]

The solution might be spending differently or changing other things that are budget neutral, such as the curriculum.

But in 90% of cases throwing money at it will help most problems a politician will face. More teachers or better teachers is doable without more money but it's hard. That means you need better school administrators that will attract and develop good teachers - but it's the same argument again - how will you get those?

The objection might be that it's not the most efficient use of money - which depending on your political views might be more or less terrible.