Talk about drawing power. In the movie ''School of Rock,'' Jack Black uses a large blackboard diagram to educate his young charges about the history of rock & roll. The complex chalk time line receives only a few seconds of screen time, but it took director Richard Linklater and production designer Jeremy Conway two weeks to sketch it out. ''Making that board was one of those ideas I had from the very beginning,'' says Linklater. ''But, oh, God, once I finally got there, I realized it was a really daunting task.'' The pair's music map covered an entire blackboard, but just a portion appears in the film, during a montage of classroom shots. Still, it's an ambitious attempt at pop pedagogy, going all the way back to proto-rock icons like Ike Turner and encompassing obscure Linklater faves like the Butthole Surfers. Being a music obsessive, the director needed only a few reference books to research his history lesson, though he did solicit input from the cast. Unsurprisingly, Black was tenacious about including Ronnie James Dio, the metal screamer beloved by his band, Tenacious D. As Linklater points out, ''Jack can be pretty, uh...definitive.''