What was the name of cartoon show that had a blue dog who pretended to be boy and went school?

You're thinking of Blue's Clues, a popular children's show that featured a blue dog named Blue who interacted with the show's host, Steve (and later, Joe). While Blue didn't pretend to be a boy, she communicated through barks and other dog noises, and Steve would use those clues to solve puzzles and learn about the world.

Blue's Clues was known for its educational content and interactive nature, encouraging viewers to participate in the puzzles and activities.