Kids. They grow up so fast -- even rock-star kids.

Last time we heard from Avril Lavigne, she was a teen tomboy, jumping around in ties and tanks while singing crunchy bubblegum rock about sk8er bois, complicated posers and junior high crushes. But now, that's all, like, so yesterday.

Avril was barely old enough to drive when she wrote her first album, Let Go, which sold a whopping 14 million copies. Today she's almost 20. And while she may not be a woman yet, she's no little girl anymore. She's been around the block. She's had her heart broken. She's figured out a few things. And like anyone her age, it's all made her a little smarter, a little sadder, a little more mature and independent.

That subtle but significant growth is clearly visible on her sophomore album Under My Skin, in stores Tuesday. Granted, on the surface, there isn't a radical difference between her first CD and these dozen cuts, most of which were co-penned with Winnipeg singer-songwriter Chantal Kreviazuk or her hubby, Our Lady Peace frontman Raine Maida.

Avril still specializes in radio-ready pop-rockers and girl-power ballads. She still juices her pop hooks and melodies with metallic guitars and arena-rock rhythms. And she still writes about boys she wants who don't want her any more, or vice versa.

But as reflected in Avril's vaguely gothy new look, these tunes are a shade darker and starker. Chantal's influence is easy to hear in the rich keyboards, moody melodies and contemplative grooves that underpin cuts like Together, Forgotten and the poignant Slipped Away, about the death of Avril's grandfather.

Lyrically, Lavigne's viewpoint is more cynical, if tempered by the contradictions of teenage personality. Sometimes -- like on the romantic rock of Fall to Pieces -- she's the girl who just wants to "cry in front of you." And sometimes -- like on the boys-suck pop-punk of He Wasn't -- she's the ticked-off chick who spends the weekend sitting "on the bed alone / staring at the phone."

But more often -- like on the anthemic Don't Tell Me -- she's the young woman who knows she's "better off alone anyway" than giving it up to a jerk who just wants to get in her pants.

Parents ought to love that. And why not? In today's submissive prosti-tot pop world, a teen role model who keeps her clothes on -- or even bothers to wear any in the first place -- is a refreshing change.

So sure, Avril may be growing up. And she still has a long way to go. But it Under My Skin is any indication, she'll probably be OK.

Track Listing
1. Take Me Away
2. Together
3. Don't Tell Me
4. He Wasn't
5. How Does It Feel
6. My Happy Ending
7. Nobody's Home
8. Forgotten
9. Who Knows
10. Fall to Pieces
11. Freak Out
12. Slipped Away