I wonder the name of this illusion

Those are 9 year old max.
I do remember in first grade looking at 4th grade kids and thinking that they are so old, they looked like 17 year old to me, and years later seeing 5th grades, they are so small, I’m the shortest in my class and am still double their height.

My theory, to why Younger people look exaggeratingly young and old people old, it’s probably just so the CPU can handle all of it better

and when its the 20s you can not tell anymore. moreso in 40s and 50s