Well yes, you have to spend the money wisely. How could we construct a system so that we have 2x as many teachers (thereby halving the classroom size)? That would have a lot of good second-order effects beyond test scores.
So why has per-capita student spending doubled since 1990 (adjusted for inflation) without any increase in test scores? Why haven’t we been spending the money wisely?
Student to teacher ratios have continuously decreased and are about half of what they were in 1960. Data on the results is mixed: https://www.brookings.edu/articles/class-size-what-research-...