First off, it takes a lot for a show to keep me invested for 16 episodes; I do not complete most of the shows that I watch because I often lose interest, and, after a week of working hard, I often don't feel pushed to pick up a show again on the weekend when I have time to watch TV. I am still surprised this show kept me captivated for all of the 16 episodes. I kept coming back every weekend (it's the only time I can watch). Many people don't seem to like the show or appreciate it, so let me clarify who this show is meant for.

This show is meant for:
-People who like slice of life: Nothing much happens in this show; you just go about 4 teenagers living their lives at a vocational school. All four have dreams, and we witness them work hard to chase what they want in life.
-People who like to see relationships slowly unfold: This is especially true of the second couple. You see them become friends; and then you see them get closer to each other. You actually see them fall in love,and you understand why they fall in love with each other. This is the highlight of the show for me. There is no love at first sight or rushing of feelings here; both of the romances are sweet and portrayed with sensitivity.
-People who want to see relationships done well: There are no silly breakups; there is no toxic behavior or selfishness. You get to see 4 teenagers facing their feelings head on, acting on their feelings, and being respectful of each other's wants. I also loved that no one allowed their feelings to impact their dreams; both FLs stood by their guy; they were loyal and loving. That never impacted their attention to their futures, and I loved that. Your romantic relationships should never get in the way of your ability to make a future for yourself. The men were also very loving and respectful to the woman in their life. They never over-stepped or pushed, and they always respected what their girlfriend wanted.
-People who want to see characters develop: In the beginning, Youngjoo was a sullen kid, angry with everyone, and friendless. By the end, he admitted to his faults; he encouraged Seoyoung to chase her dreams; and he had a friend group who had his back. In the beginning, Seoyoung was single-minded about going to college. I loved her ambition, but she was the type to give up everything to achieve her dream. Now, she realizes that achieving one's dreams at the cost of someone else is not worth it. She can go to university without having to ruin an innocent family to do so. I love that they each brought out the best in each other. Individually, they are both better people now than when they started. I think this is what makes School 2021 special for me; they took everyday tropes, and they carried them out with sensitivity and nuance.

Do NOT watch this show if:
-You want action, drama, or anything complicated
-You want a plot that is new or creative in any way (this is a show where high schoolers act like high schoolers; you just see them go about their days.).

Not only was I charmed by the show; I would say it is one of my top 5 kdramas. You're really missing out if you don't watch it. Also, the first episode is a bit slow; give it 2 or 3 episodes before you judge.