At the start of every new semester, one or two students will tell me they took the TOEFL test without taking a class and got low scores. So what happened? They decided to take the test again, but this time take a class first. Good idea.
To get the highest possible TOEFL iBT score, I highly recommend that you take a TOEFL class. Why? For myriad reasons.
1) You can learn strategies not always taught in TOEFL texts.
2) Studying for TOEFL can seem like climbing a mountain. Yet when you study in a group, you don't feel so alone. Plus it's more fun. This, in turn, will increase your confidence.
3) You can learn from example. For example, that girl from Germany speaks so well. Great. So copy what she is doing. And that guy from Peru writes such good essays. Great. So copy what he is doing. Like Picasso said, "Good artists borrow. Great artists steal."
4) Finally, and this is key, if your instructor is a native speaker, you will understand how academic English is used in its proper context. If you study alone, often you will not understand the context of new words, especially idioms
5) It's cheaper.
The Pro.