On the heels of a season that left the WB at the bottom of the ratings heap, chairman Garth Ancier called his network’s long-standing strategy of targeting teens a mistake and acknowledged that he is looking to attract older viewers this fall.

Although younger viewers vanished from all major networks this season, the problem has been particularly egregious at The WB, which has targeted the 12- to 34-year-old audience with such shows as “Charmed” and “Smallville.” Young adults, however, have been flocking to cable, video games and the Internet.

This fall, young actors such as Chad Michael Murray of “One Tree Hill” will share space with veterans such as Christine Lahti, who plays the mother of a future U.S. president on “Jack and Bobby,” and comedians Jeff Foxworthy and Drew Carey.

Ancier also admitted he’s disappointed with the racial homogeneity of the casts for the WB’s fall shows.

“We are openly not happy about the lack of diversity on the schedule,” said Ancier, speaking to a gathering of TV critics in Los Angeles. “The only thing you do to fix it is to develop shows that are more diverse going forward. We did develop other shows that were more diverse but didn’t pick those up.”

In fact, the network’s most diverse cast is on the reality game show “Studio 7,” which premieres July 22, said Ancier, who became chairman of the WB in June when co-chairman Jordan Levin resigned.