Meals safe in danger zone
May I suggest investing in an insulated lunchbox and ice pack (decidedly un-sexy, but practical), or storing in a campus fridge?  These can extend length of time food is at a safe temperature considerably.

Thermoses are wonderful things; a good thermos that is filled with fully heated/cooled food and kept properly sealed will keep the contents out of the temperature danger zone for at least 4 hours.  The brand-name manufacturing site claims 6 hours in the safe zone for commercial products, with up to 16 for hot substances.  

Failing this, cheese or PB&amp;J sandwiches are pretty nonperishable.  Remember that cheesemaking was originally intended to preserve the nutritional contents of milk for prolonged periods without refrigeration, and harder cheeses stay safe for longer.  The catch is that they will exude some oil if kept warm.   A similar principle applied to heavily cured meats, which are treated with nitrites or smoked, allowing them to be safely kept at room temperature. 

A personal favorite meal for me is baguette, cheese, and a cured sausage.  If you want to go even simpler, you can have a quite satisfying meal with  a really good artisan bread and a dipping container of herbed/peppered olive oil.