Two Point Campus

As you play on each campus objectives should show up explaining how to get stars. Unfortunately you can't get all stars at the same time or (for the most part) achieve objectives in parallel.

Keep in mind, some objectives are more "permanent" than others. For example if you have two objectives, one is to have student happiness at 75% and the other is have 20 students graduate with an A grade. Don't even worry about the happiness objective until the graduate ones are done because once a student graduates, that number won't go down. Happiness however will decrease and increase in real time so just wait to increase happiness until after.

Edit: refer to my Masters Minded achievement guide for more tips