Bart didn't take his skateboard to school but had it when he left.
When Ms. Krabbapel is grieving hysterically over Principal Skinner's absence, one of the student's, a blonde girl's (Becky) outfit, which is usually turquoise, is atypically green.
principal Skinner lives with his mom. so there is no way he could have ben trapped in his garage without her noticing that's impossible.
When Bart missed the bus, he could've asked Marge or Homer to drive him to school instead of walking there which made him come late.