Three of T.J. Lane's schoolmates were killed and three others injured in the Feb. 27 shootings as they waited for a bus to take them to an alternative school, Lake Academy in Willoughby.
Lane, 17, was indicted on adult charges of aggravated murder, attempted murder and felonious assault earlier this week. Geauga County Common Pleas Judge Forrest Burt ordered Lane held on $1 million bond.
The (Cleveland) Plain Dealer reported the case likely will hinge on sanity issues.
Police said Lane admitted to the shootings, using a semi-automatic handgun he had taken from an uncle's home.