1. There is absolutely no guarantee that spending more money increases service quality, especially when (as is the case with public schools) there is no competition to discipline spending and ensure that it is funneled to those aspects of the service that are actually important to customers
2. Over the last 20-30 years, administrative staffing in public schools has grown from a small percentage of the total to about half the headcount in many public school districts, and thus likely more than half the salary budget (since administrators frequently make more than teachers)
3. Much of the increased funding is going to retired teachers who aren't actually teaching anyone

Per-student spending on K-12 education has risen steadily over the last two decades, but student test scores, and teacher salaries, are stagnant. Why hasn’t this massive increase in investment produced better teachers and better opportunity for students? The short-answer, according to a new Manhattan Institute report by Josh McGee: State and local governments have catastrophically mismanaged their teacher pension systems. The cash infusion to K-12 has been used largely to pay for irresponsible pension promises politicians made to teachers’ unions and justified to the public with shoddy accounting. . . .

In other words, to cover benefits for retirees, states need to dig into education funds that might otherwise be used to attract and retain good teachers or buy better textbooks and build new facilities. So long as state governments are unwilling to reform the blue model pension-for-life civil service system, and so long as teachers unions continue to wield outsized influence in so many state legislatures, this pattern seems likely to continue indefinitely.

Campaigns to increase spending on schools are always popular, and understandably so: Education ought to be a great equalizing force in our society and, in theory, an efficient way to invest in the future. The problem is that in many states, new “K-12 spending” isn’t really an investment so much as a transfer payment to retired employees of the public schools who have been promised untenable lifetime pension benefits.