If your impressions of Ashley Tisdale are fuzzy around the edges but include visions of singing schoolgirls, blond supercuteness, and shrieking, hysterical 10-year-olds, you'll want to check them at the door before checking out Headstrong. It's not that fourth graders won't like the long-limbed High School Musical star's hooky, happy, and at times hyper solo debut. It's just that you might, too. Tisdale, a little like Lindsey Lohan and not at all like Hilary Duff, doesn't waste time ditching her groovy-juvie reputation to reimagine herself as a red-hot starlet here. "He Said She Said" is a steamy dancefloor seduction that ought to come with a PG-15 rating ("Baby I can see us moving like that/Baby I can see us touchin' like that," it goes), and "Not Like That" mines familiar misunderstood-celebrity territory in a way that's less whiny than worked-up. The thing is, it all sounds pretty good--from the head-bobbing urban beat in "Be Good to Me" to the fuzz and boingy effects on "Over It," Tisdale proves her appeal is not limited to junior proms. Which is not to say she doesn't leave a little something for fans who still dot their I's with circles: One of Headstrong's strongest numbers, "Unlove You," is tailor-made for belt-outs in pastel-pink bedrooms