It is young, especially amidst a global bloody pandemic as there were extended periods of lockdowns all over the world.
Normal is a strange word nowadays.

Yes seniors graduate at 17 or 18 years old this is completely normal

17

He must have a late birthday.

Normal. I was 17 when I graduated HS. If I remember correctly I must've started the senior year at 16 just few days before my 17th birthday since I'm a September baby.

I was 17 at graduation

My son graduated and was 17 .so I'd say normal
I was 17 as well

Dan was 18 when he graduated this year

Yes, for most. Some a bit earlier or later.

We have a different system, here you can graduate at 17, 18 or 19 depending on the type of the school and whether you were born early or late in the year.

My daughter was 17 when she graduated.

I was 17 at graduation too

August birthday?

Both my boys were 18

Quite.

17-18. I'm sure he will be ok

I was 18 when I graduated. Though I have friends that were 17 because they have summer birthdays.

I was 17 all of senior year butmy birthday is in June right after the end of the school year.

Among my friends, some graduated at 17, some at 18. It's no biggie. The natural variation in maturity of HS seniors is pretty large and not entirely age dependent. However, IF he's struggling in his classes, lack of maturity might be part of the reason.

I was 16 when I started Senior Year, 17 when I graduated. I was one of the youngest in the class except for a few people who came from places where they could skip a grade. I kind of wish my parents hadn't started me in Kindergarten a year early, though. But it wasn't horrible.

My youngest biological sister graduated at 15. I have 4 stepsister younger than her.