"His parents had just moved" joke

His parents had just moved to town, and it was his first day in first
grade at the new school. He was really nervous, but he didn't do so badly,
he learned to count to '50', when most of the other kids could
only count to 30, (some kids got to 35, but our boy got all the way to 50
and only missed a couple of numbers)
Our hero was so excited, that when he got home he told his dad
how well he had done in school. His dad said "Son, you did so well
becuase you're an [ethnic]."
The next day the kids learned the alphabet in school. Most of th ekids got
as far as 'M' or 'Q', but our hero got all the way to 'Z', and only missed
a couple of letters.
That evening, bursting with pride, he told his dad how he had done better
than all the other students
on the alphabet. His dad said "Son, you did so well
becuase you're an [ethnic]."
The next day, in gym class, our hero notced that he was a bit more
"developed" than any of the other boys. That night he asked his dad
if was bigger than the other boys because he was an [ethnic]?
"No, son," his dad told him, "You're bigger than the other boy becuase
you're eighteen."