Should I discuss bad grades?

So one of the essays on the Common App this year that I am considering answering is:

“The lessons we take from failure can be fundamental to later success. Recount an incident or time when you experienced failure. How did it affect you, and what did you learn from the experience?”

Take my situation: I applied and got into the Oklahoma School of Science and Mathematics for my junior and senior years. During the first semester of my junior year, I received pretty bad grades, many Bs and even a C due to not transitioning to the new environment quickly enough and overall complacency. However, after seeing my grade report at the end of the semester, it hit me that I needed to get it together and pull my grades up. I ended Junior year with 5 As and 2 Bs (compared to 1 A, 1 C, and the rest Bs first semester) and got 5s on the 3 AP Physics tests that I took. Is this something that would be good to go in depth about for this type of essay?

It is a possible essay topic- However, you really need to be careful that it doesn’t read as you trying to excuse your bad grades. If it is going to work, it needs to focus on the lessons you learned (not the grades you got), what kind of person you are now, and how such growth will help you in college. It’s not a bad essay topic per se, you just have to go about it the right way.

When did a “B” become a bad grade? From your subject line, I expected you to be worried about Ds and Fs. Relax.

It could work but honestly seems a bit unnecessary. They have access to your transcript and will be able to infer that the switch was hard and you adapted. IMO the best essays show something beyond the rest of your application.

I agree with most of the above. Show an aspect of yourself beyond letters, numbers, etc. Grades are only detail, while important, do not paint a full picture whether they are all As or all Cs.
There is an “Additional Information” section which could be used to expand on how transitioning affected you, though I would make sure to not sound over-dramatic or anything, just be upfront and tell what you learned from the experience.