Don't be such a lump of school and listen to me.
lump of school
idiom Slang
Cockney rhyming slang · East London
fool
Origin
The market stall holders felt that the sooner the boy stopped reading books and gained practical experience the better.
He acted like a total lump of school when he tried to fix the engine without any tools.
Despite his expensive education, he proved himself a complete lump of school by ignoring the obvious warning signs.