While this might be the deadliest school shooting in our nation's history, it is not the deadliest mass killing in a school. That occurred over 50 years ago, in 1927 in Bath Township, MI. A local office holder, upset because he had not been re-elected, killed his wife, then blew up a school, killing 38 children and 6 adults before blowing himself up.
The assumption that a gun ban would stop school killings is a red herring. Those with evil intent will just turn to more lethal methods.