Qualifications
There's two basic routes to becoming a sex educator: certification or university degree. If you go the university route, you'll wind up with some pretty intense, in-depth knowledge of sexuality. You'll know the Kinsey scale like the back of your hand. And you'll get to bask in the glowing prestige that that degree gets you. But you'll be majorly in debt. And you won't have any real life experience to put on your résumé boast of to employers.
If you go the certification route straight away, you'll get your name included in a directory of sex educators (like the American Association of Sexuality, Educators, Counselors, and Therapists) for the price of a nice pair of boots, and sidestep a whole lot of debt. With the time that you're not in school, you can also get a jumpstart on that internship at a clinic or entry-level teaching job. But your certification might seem flimsy. After all, you bubbled in a couple of answers correctly on a scantron. You didn't take any courses or complete any training. That's why more and more sex educator wannabes are racking up the bachelor's and master's degrees either in human sexuality or in related fields, like psychology, education, public health, and so on.
Decisions, decisions. The best plan is one that balances study (whether at a four-year university, at a community college, or into the early hours of the morning on your own) with some sort of internship (working at a crisis hotline, or as a teacher's assistant).