Singing rodents Alvin, Theodore, and Simon return in this follow-up to the 2007 hit. Smarter than its predecessor, the movie aims for the High School Musical market as the chipmunks’ guardian (Jason Lee) insists they get an education; their new babysitter is an LA slacker (Zachary Levi of the TV series Chuck) whose arrested development corrodes his already negligible caregiver skills. David Cross returns as the trio’s former record promoter, now unemployed and staking his comeback on a rival group, the all-female Chipettes, that comes across as a cloying knockoff of Destiny’s Child. Director Betty Thomas (Doctor Dolittle) keeps the pace brisk and hits some good notes, but not enough to boost this comedy above kid stuff.