Dream interpretation?

This dream could be telling you that there is an important life lesson that you still need to learn. It could be something that you need to develop, like a life skill. You might need to give yourself permission to take the time to focus on growing in those areas. This is probably more of a life lesson than a school lesson. 

Have you done anything new since your college graduation?   Your mind has no new outlet to dream about.  School is safe as it is familiar to you. Once you begin a new Life, or employment, new events will happen and you will find you dream of these things.  But it is perfectly normal to dream of school now and then, because it is an important part of your Life. 

There are two different types of schools.

The earthly schools like HS and college. There is also the school of life where you learn about your purpose in life, God's calling on your life, etc.

In the same way you are born, mature and grow physically, you also do spiritually:

1 Peter 2:2 "Like newborn babies, crave pure spiritual milk, so that by it you may grow up in your salvation.

Some people can go through education and college, but they still remain a baby spiritually. Have you heard of people "that never grow up".

If you are dreaming about school even though you are done with it physically, that means you are still in learning mode spiritually.

Repent of your sins and ask Jesus in your heart, and then ask HIM for the Holy Spirit, that His Spirit may lead you into all truth. The Holy Spirit is your greatest spiritual teacher. Then read the Bible. You will find your own personal life in there like I did.

idk. maybe u try too hard in ur school that it's already in ur subconscoiousness