I have been suffering from depression too, dispate that and misterily I continue to do good at school. But see for me it is really a mistery because I feel the same way as you do. I feel totaly stupid, I can get focus or memorize things. But I guess I do fine at school because test are multiple choices. But I wonder if it would be different if I felt fine. Cause paper works and presentations are hard for me to do. My syster had been depressed, she got out of it. At that time she failed the year, she is now doing much better at school. Don't put so much pressure on your self, failing is not the end of the world. Think of it as a time off you have to get your self on your feet. You don't have nothing to prove to anyone, you're sick, one of the worst ilnesses in my opinion, because it takes you so much life. But depression is a certain way your body finds to tell you that you need to slow down, you need to rest. Not for your entire life, just for some time. If you feel you can't handle it talk to someone else. Are you taking meds? Maybe you should. They didn't work for me but they worked for lots of people that I know.
How wish you the best