The setting for Sixteen Candles is more generic than that box of birthday cake mix you bought because you're too lazy to make one from scratch. (Hey: a cake is a cake is a cake.)
Sixteen Candles is similar. It's not Ridgemont High like Fast Times at Ridgemont High or sunny southern California like Clueless. Sixteen Candles is supposed to be a simple, generic Anywhere, U.S.A., making it all the more relatable to anyone watching. There are no identifying landmarks or mascots, so you can imagine these events happening at your school.
However, the film had to be shot somewhere, and its locations come from Chicago suburbs like Glencoe, Evanston, and Skokie, Illinois. Although John Hughes attended school at Glenbrook North High, he wouldn't actually use that school until Ferris Bueller's Day Off. (Source)
Instead, Old Niles East High was used as the location for Sam's school. And if you want a Sixteen Candles themed wedding—and you know you do—the church is Glencoe Union Church. (Source)