I need to develop the courage to be more straightforward to my friends?

You seriously just need to tell them that you really want to do stuff with them, but school has to come first. One of my best friends is like this and I'm always telling him to relax. But I understand that he's worked so hard to get where he is now that he deserves to be left alone to get what he needs done. Good luck with the scholarships and with the friends. I think you'll be able to find the courage to talk to them. : )