It's... kinda hard not to notice someone who is profoundly retarded. Especially if you spent over ten years in the same class as them. Like, I'm not one to disparage the mentally-handicapped, but you [i]know[/i] when someone is suffering from mental retardation.

In order not to notice Jerry unintentionally, a character would have to spend nearly every class session nose-deep in their books while wearing ear plugs.