John Petrucci, John Myung, Mike Portnoy and Derek Sherinian all went to the Berklee school of music in Boston, MA. Berklee is a music-dedicated school that has produced the likes of Steve Vai, Al Di Meola and Chris DeGarmo.
When at Berklee, JM, JP and MP all left school to concentrate on the band after the first year, so none of them graduated (Although a common rumor states that Dream Theater holds doctorates in music, which isn’t true).
Jordan Rudess attended Julliard in New York from the age of 9, and Kevin Moore went to SUNY Fredonia, in New York.
Mike Mangini went to Bentley University to pursue a major in Computer Science. He later changed his mind and focused on a career of music. At the time of being hired by Dream Theater he was working as a faculty member of Berklee.
The two Johns and Kevin also went to high school together; King’s Park High School in King’s Park, (Suffolk County) on Long Island.