What pop songs are 2nd-6th graders likely to know?

I work at a museum, and we’re currently hosting an exhibit on popular music in American history from the 1770s to the 1930s. I’ve put together a program for the school groups that come to see the exhibit, but I’d like to start off by talking about what songs are popular today. My CD collection runs to Tom Waits and kd lang; I’m not up to speed on current bubblegum pop. So help me out here. What songs are popular among the elementary school crowd?

Based on what my ten year old sister likes, most of them would probably know anything by Hilary Duff. I think her most popular song was called “I can’t wait” or something like that. Hey, ya by Outkast is also pretty popular with kids now. My sister also likes the Milshake song by Kelis, but that might not be appropriate.