Your country does not have enough schools or high schools. You need more to educate more people at a high level and build your economy. Keep building schools even beyond the numbers shown as needed. You will need more teachers and you can take care of that by increasing the education priority for teachers. The education index depends on the school index, the high school index and the university index. Make sure your school, high school and university indexes are in the range of 120 to 180 for good results.