A reasonable person, lets say a neurologist or developmental psychologist, might very well say there are differing levels of intelligence between girls and boys. It depends on what you're measuring. When they study intelligence closely enough, there are absolutely differences between the sexes. I don't think it's sexist to say that girls are generally better at interpersonal communications than boys (a form of intelligence). Even if it's that debatable (and I'm sure it is), moving from a disagreement on opinions to a title IX complaint is not warranted.
And in a class about neurology or developmental psychology, putting it to a question, "are boys smarter than girls?" and then using that to explore different kinds of intelligence, is a very different thing from a professor in an unrelated field declaring, "It's my opinion that girls are less intelligent than boys, blah blah, office hours at 3pm on Wednesdays, etc.."
One is ok, the other suggests a bias that's going to cut half the class off at the knees.
