I wrote out a big response, but it summed to this.
For daily mj usage in school...
There is a strong chance that it will hurt your academics due to loss of motivation.
There is a stronger chance that at the very least, it will do you no favors.
There is a small (<5%) that it will give you a noticeable positive impact. Like how Nyquil makes some kids twack out and go through the roof like they're on meth.
The thing with school is, you work hard, study, take the tests, get an A, and ding... get you happy brain chemical reward. When you pipe in your sense of well-being in before you go to the first class, then it's harder to make it in that day.
I do it. My grades are good. I have OCD like crazy though. I have calendars and post-its all over the place, and now that I mention it, I've been washing my hands more, lol. Seriously. I've "weeded out" and forgotten very important meetings, exams, etc. and had to lie my way out of a jam which I don't like doing. Too many lies make a liar. There is a level of paranoia that comes with being a medicated professional that you may not like the flavor of once you get a taste.
That said, I'm envious of my buddies who are construction contractors. They make 20 bucks an hour to build things and smoke out all day. Talk about a dream job...
So as you can see, mj poses all of the same risks at the same levels as Xbox Live does. Don't laugh, how may parents do you think have spent $$$$$$$$$$$$$ for their kids to play Halo for 5 years and get a degree in nothing?