Do you like kids? A lot?
If you’re really crazy about math or science or English, but you don’t particularly like kids, you will probably not like teaching with TFA.
This one sounds obvious, right? But there are a lot of people who love what they studied in (or outside of) college, and they want a job that will allow them to go on studying it. They love the modern novel, so they want to do something related to English literature. They like complex proofs, so they want to work with pure math. Of course, jobs that allow them to study the academic subjects that they love are few and far between, and teaching begins to look attractive. It allows them to work with math or English or history all day long, and not only that, but to teach other people to love math or English or history. And there are all those hours after school and in the summers to spend on private study!
No. No no no no no no no.
If you decide to join Teach for America, do it because you want to teach kids, not just because you want to teach math, French, science, or literary theory. The chances are good that, if you become a TFA teacher (or any teacher, really), most of your students will have little to no initial interest in what you teach. They will not bring to the study of lipids or the analysis of novels the same enthusiasm and energy that you do. Many of them may regard school as a prison, your classroom as a cell, and you as their warden. Your lessons? Just more instruments of oppression. Some students will take pleasure in deriding the subjects that you obviously find most interesting.
This is not to say that you’ll never get your students interested in anything. But they won’t start out interested. Often the most effective way to gain their attention, and their respect, is not to rely on the intrinsic interest you think everyone should have in mitosis or the rain cycle or ancient myths, but to let your students know that you’re interested in them, that they matter to you, that you know them as individuals. Once your students know you care about them, they might be more inclined to care about what matters to you, such as American history or matrix algebra. This is where liking kids comes in, and this is where you might have problems if you’re teaching because you like academic study but not so much students.
You’ll also probably find that there’s very little time to advance your studies while teaching. Teaching, especially for a first-year corps member, absorbs a LOT of time and leaves little energy for reading, writing, or even intensive thinking. It often involves introducing very basic concepts to an unreceptive audience over and over again. Over time, you may start to fear that you’re forgetting more about the subject you love than you’re learning.
If you love a particular subject above all else and don’t care as much about kids, consider grad school. Reconsider TFA.