As a former middle school/high school teacher, who now subs, I totally agree with the above suggestions!! Since school is now out in most parts of the country, you could start now with the listening in and - if you need more - follow-up in the fall with the sitting in. (Be aware, many districts will require a background check to be done by the local or state police before you're permitted to spend time within a classroom. You might check into that now, so you don't have to wait to be cleared once school resumes.)
Best wishes, Brenna!!!