It is my opinion that those raised on Rock but now wanting to get into "Classical" (just so you'll know, Classical is actually one era/style of "serious" music, though commonly used as the name for all of it), would do well to start with the Baroque era. The tempo's are brisker, the movements shorter (often song-length), the energy more kinetic---all traits of Rock music.
J.S. Bach, Handel, Pachelbel, Rameau, Scarlatti, and Vivaldi are the major Baroque composers. You're gonna love it!