I’m a sophomore, and the language arts classes were overflowing in my school so they opened up a new period with the better teacher of the 2 teaching at my school; however, there are only about 16-17 people in my class. I always make a lot of friends through Language Arts classes, since my most endearing personality comes out in those classes haha! Did I make a mistake switching to the teacher that teaches more, and gives out more work, but teaches you how to write, but the class is only consisting of about 16 people that barely participate leaving me to do all the participating?
No. You may or may not keep your friends after HS, but good writing skills will be with you forever.
FWIW, in my HS 16 students would have required a new section to be opened up and now in college, many classes have fewer than 10-12, so you it’s good to get experience “carrying” the class early.
Not at all! In the end, getting a better education is what matters. Besides, it’s a great opportunity to meet new people!
No, you did the right thing. You’ll make friends in other classes and in your EC’s, but since having strong English skills is foundational, this is definitely the best thing you could do for yourself in the long run. 
Congratulations on making a good choice.
I think you made the right choice! She’ll definitely notice you if others aren’t participating.