"Nerd" doesn't mean "smart". There are genius level jocks and nerds who are so dumb they need velcro shoes.
Nerd means that you don't participate in any level of physical activity and are an outcast from all social groups because you'd rather be engaging in an obscure interest. It has NOTHING to do with being smart.
The people in Revenge of the Nerds aren't nerds, they're just smart.