One problem I found is no one was going to college. The grade school and high school would be packed, but the college would have very few students. It's a really strange dynamic and doesn't make a lot of sense, but once I turned off my high school the attendance at the college went up. It is either that or your population is too high (therefore not enough are going to school) and the community college needs more additions to it.
It not just the building that ups the tech, it's the population actually going to the high tech institutions.
Somebody else may be more versed in what it takes to up your college population. IIRC, low income is happy about grade school, mid income happy about high school, and high income happy about those 2 and college. Yet I am not sure if that means low income only sends kids to grade school, mid income only high school, and high income sends students to all 3.