Uh, that's not the definition that biologists use. Kingdom animalia includes humans. (along with fish, birds, reptiles, insects, etc.) We're mammals.
Also, a vast majority of people use this definition of the word "animal" when referring to the animals themselves and only tend to use other definitions (which typically ends up referring to non-human mammals or sometimes humans the speaker find distasteful for whatever reason) specifically when contrasting them to so called "civilized" humans.
You can look up the word "animal" in a dictionary and I garuntee you the kingdom animalia style definition will be the first one you see under the noun form of the word with all other definitions (the ones that exclude humans or insects) coming later. Dictionaries typically order their definitions by usage when there are multiple definitions of the same word.
This, and also not "doing drugs" and going to college are also difficult. Mind altering substances can become a normalized part of social interaction (I live in America and my favorite illustration of this is talking about caffeine. Sure, the chance of developing an addiction is lower, and the consequences of a dependency are less severe, but telling a kid "don't have caffeine ever, it's bad" is just insane, they might be able to avoid it for a while but the environment itself is trying to shove it down our throats).
College doesn't have the same issue but it's got its own set of issues. And all three of those things become more difficult when you stack their problems.
Framing things as either falling into "a choice" vs "not a choice" ignores the fact that pretty much all things have at least some elements of it that we can and can't control.