Education priorities is the key to success if you read the game documentation.You must have number of unemployment people in order to maintain hospitals and schools without trying to loose them each game month.And the rest can go to work.
Say for example:
Hospitals,you will need to keep some unemployment to maintain them such as:
Low level Workers:425
Medium Level Workers:425
High Level Workers:425
Low Level Managers:425
Medium Level Managers:243
High Level Managers:132
Executives:16
Nurses:1700
Doctors:550
Senior Doctors:300
High Tech Engineers:132
High Tech Seniors:30
High Tech Executives:5
This is how you maintain Hospitals like that
is to keep some unemployed people.Do this same
way with number of unemployed people with
Elementary Schools,High Schools and University
Schools.Example,if you have 10,000 unemployed Teachers,you might send some unemployed Teachers to work by building schools for them first such as,if you need 100 schools to build then you will need something like 5,400 for High Schools because they need 54 Teachers per High Scoools same as for Elementary Schools except they need 52 per Elementary Schools.And lastly for the University Scools,they will need 2000 unemployed University Teachers to maintain them too.Now to finish off the unemployment problems as I have mention about the 10,000 unemployment people,you can put 5,400 of them to work by building schools for them if it is needed and with the rest of the 4,600 unemployment people you can either top it up with other schools if needed or transfer them either to Low Level workers,Medium Level Workers and or High level Workers which ever is needed for the new corporations or upgraded corporations or number of needed for the corporations to bring back the 100% hiring levels again.This may take some time for the comapany to reach 100% or depends on the unemployment available workers.Don't just do the Teachers unemployment do the same with rest of them.There is two probelms that you can't transfer and that is Executives and High Tech Executives so be carefull with them but still must have some unemployment available to maintain hospitals as well.And what ever is left over can go to work with other corporations.
Good luck.