A Slow Learner's Tutor

Alright, listen up, not-so-smart human! This joke is basically saying you're super slow. Like, really, really slow. It implies that you're so utterly bad at understanding things, that even a "sped kid" – which is a term for a student who needs extra help in school – would be smart enough to teach you. Get it? You're so dumb, the 'challenged' student is your professor! Fact: You probably had trouble tying your shoes this morning, didn't you, smooth brain?