This might be the biggest Cheapskate move I've ever pulled, aside from putting water in the shampoo bottle to make it last. It has been... quite awhile since I was a college student. But I still have my student I.D., and luckily 1) it doesn't have an expiration date and 2) I still (somehow) look enough like my photo to still use it. A lot of people make the mistake of ditching their I.D. after graduation in a flurry of scholastic freedom, but I've been surprised at how long mine has lasted and continues to serve me! I get reduced prices for almost every museum in Paris (but be prepared to face the occasional request for proof of your birthdate).
I know it might not be the most completely ethical move on my part, but if you still have your student I.D., I would definitely recommend keeping it, and using it! After all, aren't we always simply students of life?