Whenever you feel ready and want to. There's no cut off age in dating. My aunt dated in her 40's and found a man and marriage and was very happy. She passed unfortunately but still. The message is: do what makes you happy.
Start dating man don't waste your life, its take experience to learn what you are willing to put up with and what you are not willing to put up with. You learn about sex, family life, addictions, behaviors and lots of other stuff
It gets harder and harder the older you get, even if you're experienced, let alone if you're not experienced, just giving you the honest truth... Plus there's no good reason you can't have a girlfriend and do well in school at the same time.
It's never too late, and it's totally up to you when you wanna start. I mean my Grannie started dating when my gramps passed away. If she can do it, so can you! Most people have some relationship experience by this point in their lives, but not all. Take your time and find someone you like, dating is all about banging *cough* I mean getting to know someone. Take your time and figure out who are the people who you'd be interested in getting to know better