“Highschool kids” in American TV shows

I have been recently watching the new season of the show ‘One of Us is Lying’. As I was watching the show, it reminded me of one common trait in American TV shows set in High School. None of the characters look like they are in High School.
Look at this poster. All of these four characters are supposed to be in high school. But none of the characters look their age. It seems like they didn’t even try. This is with most shows. If I am not wrong, the characters in the TV show ‘Riverdale’ are also supposed to be in high school. But as usual none of them look their part.
I think the only show where the actors actually look their character’s age is Stranger Things. Firstly, it is definitely a much better show than the other two. The casting is also done better. You don’t feel awkward seeing the characters go through their highschool days. Other shows should learn.