The drug scene is as big as you make it. Unless you're feeling brave or know certain people, it's difficult to go around looking to buy drugs. The most harmful (but also the most popular) illegal drug is marijuana, which is something that you'll find more frat boys than Collins girls doing. Students with prescriptions to drugs like Adderall will sometimes sell their pills, but most students take it to keep them awake for long hours of intense concentration and last-minute cramming. This usually backfires and is a bad idea.
There really isn’t pressure to do any kind of drug. Alcohol is by far the most widely accepted, but even then it is really only with upperclassmen or at frat parties. Alcohol isn’t that easy to avoid because everyone is looking for something to do, and it always seems to involve drinking. Exceptions are often made, though, by dry frats who throw parties, on- or off-campus with nothing more than Dr Pepper. The biggest thing is that drugs will only be as visible and involved in your life as you let them. The Baptist heritage of the school does not mean that drugs do not exist. After all, this is college, so drugs can be found if you really want them. But the religious affiliation of the University does provide support for students who are not interested in doing drugs or drinking.