1) Set high academic standards for all of our kids, supported by a rigorous curriculum.
2) Greatly improve the quality of teaching in our classrooms, supported by substantially higher compensation for our best teachers.
3) Measure student and teacher performance on a systematic basis, supported by tests and assessments.
4) Increase "time on task" for all students; this means more time in school each day, and a longer school year.
Everything else either does not matter (e.g., smaller class sizes) or is supportive of these four steps (e.g., vastly improve schools of education).