schoolboy
n.a boy who goes to school. You use this word to describe a young male student, usually at a primary or secondary school.
n.a male child or adolescent who attends school. Often used attributively to describe simple or basic errors that a more experienced person should not make.
“The schoolboy carried a heavy backpack to class.”
“The local bus was crowded with schoolboys in their blue uniforms heading home for the day.”
“The veteran defender was embarrassed after making a schoolboy error that allowed the opposing team to score in the final minute of the match.”
Often used as a modifier in the phrase 'schoolboy error' to describe a basic or careless mistake.
From school + boy.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.