Complex sentence: O'Connor High School has one of Texas' largest marching bands and was led by Mr. Wallace Dierolf from its conception until 2004, and is now headed by Mr. Roland Sandoval with the assistance of Mr. George G. Garza, Mr. Wesley Perkins, and Mr. Eric Eaks.
Split into simpler sentences: O'Connor High School has one of Texas' largest marching bands and was led by Mr. Wallace Dierolf from its conception until 2004. It is now headed by Mr. Roland Sandoval with the assistance of Mr. George G. Garza, Mr. Wesley Perkins, and Mr. Eric Eaks.