initiative. Throwing more money at current teachers won't necessarily make them teach any better within the current educational ecosystem. I do think you would see good results, though, if you gave teachers a significant pay increase, more autonomy (your words) to teach and evaluate their students in their own way, and also made teachers accountable for poor student performance.
This type of three prong approach has its own issues to get over, but I think it would provide the quickest tangible improvements for quality of education.