I took regular English first semester freshman year, then switched to Pre-AP second semester.

Recently, I’ve been worrying quite a bit about a small mistake I made a while ago, in Freshmen year (I’m a Junior now). I took regular English for a semester then, because it was rather easy, switched to Pre-AP Enligsh for second semester. I’ve been trying to have the most rigorous course load possible (10 APs, 6+ Honors), and I’m worried that this little mistake won’t be good for me in the admissions process.

Is this stress that I’m having legitimate, or is this not a big deal at all?

Why is this a problem at all? If you grade was bad, it was a freshman year grade. If you grade was good, then I don’t think that you have any problem at all (at least not with what you have mentioned).

Not a big deal at all. Actually it is good, because you realized you weren’t being
challenged and switched to a harder class.