James Hibberd

Fox won its first in-season Thursday with regular series programming in 15 years last night, thanks to decreased competition and the promotional power of “American Idol.”

Fox’s regular Thursday night lineup of “Are You Smarter Than a 5th Grader” (3.7 preliminary rating among adults 18 to 49) and “Don’t Forget the Lyrics” (3.4) hit season highs. The shows were promoted earlier this week during “Idol” and benefited from airing against mostly repeat programming.

NBC was second, starting with comedy repeats of “My Name Is Earl” (2.4) and “The Office” (2.2). At 9 p.m., “Celebrity Apprentice” (3.9) was the highest-rated show of the night, and at 10 p.m. the final original episode of “ER” (3.5) won the hour.

CBS had repeats of “Without a Trace” (1.8) and “CSI” (3.5) leading into an original “Without a Trace” (3.3).

On ABC, an original “Ugly Betty” (3.0) was followed by a repeat of “Grey’s Anatomy” (2.5) and an original “Big Shots” (a series-low 1.8).

The CW aired repeats of “Smallville” (1.1) and “Supernatural” (0.9).