
he just recently became a high school student, so what difference does it make?

http://www.mangago.zone/read-manga/may_flowers_are_not_blooming_yet/uu/may_flowers_are_not_blooming_yet-chapter-1/7/ The kid clearly asked are you not from this Junior High because he didn't know about his mother's CEO status, fyi.

As Psychodaria said, his friend asked the other kid if he was from a different affiliated junior high school. Meaning, they're not in high school anymore. He's in high school.
I'm the translator, I would've noticed if he ever said anything about being in junior high or only being a recent high school student. His age is at minimum 15 years old and maximum 18.
Also, he clearly stated: "I am already a high school student."
http://www.mangago.zone/read-manga/may_flowers_are_not_blooming_yet/uu/may_flowers_are_not_blooming_yet-chapter-1/17/
Ughhh I really wanna like this story but since I know that 23 seme and the uke is in junior high so he's 14 max, I can't help but think of pedophilia and it turned me off from the whole story.