you're a numbskull

you're a numbskull

You are really stupid. If you think no one will catch you cheating on your exam, you're a numbskull and deserve to get caught.
Farlex Dictionary of Idioms.
See also:
  • on one's
  • on someone's
  • out of one's
  • (I've) got to go
  • save someone's skin
  • (Have you) been OK?
  • #dead
  • other than
  • other than (something)
  • pillow-biter