I just started taking the BBST Foundations class. It's very much an introduction to software testing course. So why am I taking a basic software testing course that frankly I could have passed years ago?
Because it's helpful to go back to basics sometimes.
Look at it this way: the guy who hit the most home runs in the entire baseball league last year.... still goes to batting practice. He's really really good at batting, but he shows up and works on the basics of his swing and his stance and his.... well, whatever else goes into batting.
Back to basics.
I go back to basics because all of the things I've learned since color and deepen my understanding of the basics. I'm good at taking a system with little to no specs and figuring out what's going on, identifying oracles, etc. (See my earlier posts about oracles here and here). Participating in a class that includes a section about oracles, I can now apply what I already know to the lessons and more easily see real world applications, real world trip ups (see for example the second link above where I've learned that oracles are only good if your customer agrees with them!), and get some new ideas.
Even if you're an experienced tester, consider taking a survey course or other testing course that looks "too easy" for you. Going back to basics can help you refine your technique and help bring in new ideas for things that you thought you already knew. Use a class to avoid a rut; it sure can't hurt!