Lies

He got setback in fifth grade, so he assumed that his age was setback as well.

I'm not sure what this is from, but I think I've worked it out... This poor kid failed 5th grade and had to redo but someone tried to comfort him saying it was hard for everyone. He would've been embarrassed at being older than everyone else so someone (possibly the same someone) told him that he was ten for two years so he could still be ten. I might be wrong or overthinking, but that's what I got.