If you're going back to school, I suggest you put your spare tube, tire levers and mini-tools in a small bag that you can easily toss in your backpack. Saddle bags will disappear in no time. Gloves are good. I use them all the time. Fenders are good if commuting by bike only. Lights are also good ideas.
Other things you might consider are a good lock (U-lock) and perhaps a pannier rack (over rear tire) good for hauling things.
I don't know how far your commute is, but it may be worthwhile to invest in a Large Camelback. That way you can keep your tools in it, carry your water, and your books in one place!
Lastly, a lightweight windbreaker is good to have. Something that folds up small and you can toss it in your backpack. Rainy rides home are fun, but rides to school and sitting in a wet shirt all day suck!
L8R
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"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming, "WOW, What a Ride!" - unknown
"Your Bike Sucks" - Sky Yaeger