Other mistake: In the 'sped' class the teacher starts taking attendance. He goes through and finishes but he never calls the main girl's name or her friend.
Other mistake: After Mary has a tin of paint tipped over her head she runs out of the school, gets on the back of Slater's motorcycle, and they ride to the pool. Mary is covered in wet paint yet none of that paint is transferred to Slater's jacket. The back of the jacket is shown clean.