School or Waste of Time?

One of my biggest worries and scares is that all this school...all this time spent studying and writing notes...will all be a waste. A lot of the times, for me and probably a lot of you...I learn these things, study really hard for tests, finish those tests..come out and forget everything I've ever learned. Like let me ask you a question...if you're in high school, do you remember the majority of the things you've learned so far? If you're in university, say first year...do you remember what you learned in high school? If you're in your upper years...do you remember what you did or learned in your first year...second year...third? Something that scares me is that all this studying will be done...just for that diploma...for that piece of paper that says I'm qualified for certain jobs...but all the knowledge will have never really stayed in my head. Another one of my biggest worries which I've voiced out numerous times is that I'll spend many years in school for a certain subject...but I'll come out and end up working and doing something that has nothing to do with what I studied in school...that'll make me feel like I wasted all those years in university...but at the end of the day...all these worries, all these thoughts, all these stresses and all these concerns...I just gotta let it all go to God and trust in Him and in His plan that He has my best interest in mind and whatever happens happens, but it'll all be in His will for me.