Take a tour of a school. Ask a teacher how much she spends on supplies.
There would be no paper or pencils if teachers didn't spend their money on supplies.
Count how many children are in each classroom. Compare the teacher's salaries with that government appointee in the principal's office or at the state level.
Nobel Laureate Milton Friedman once talked about Max Gammon's Theory of Bureaucratic Displacement. In a true bureaucracy, useful work is often replaced by useless work. And certainly useless work is compensated at a higher rate. The typical public school model pays political hacks and bureaucrats ten times the money paid to the people who are doing the actual teaching.
Above all, focus on inner city schools. Work with local governments and businesses to provide the above improvements as well as extracurricular activities for children to expand and stay off the streets.
President Trump has proposed creating Opportunity Zones in inner cities, offering tax breaks for businesses who relocate to those sections of town. Creates more commerce and more jobs. Build up the economy of an inner city and you get increased tax receipts from new property taxes. Local school boards have more to work with.
Enforcing immigration laws and getting illegal aliens OUT of these neighborhoods, as well as preventing new illegal aliens from moving in would be a gift to teachers that just keeps on giving. I subbed at a third grade class in an inner city school where one fourth of the class did not speak English. And yet, the teacher is held accountable for the achievement of those who are sitting in a room without any idea of what is being said. It's not fair to them and it's not fair to the teacher.