MIKE MOSS SAYS:      Emilie,    I think most experts on tornado safety would recommend leaving the windows alone and putting your efforts and time strictly toward getting away from outside walls and into windowless hallways and smaller interior rooms like closets and offices (not large free-span roof areas like cafeterias and gymnasiums, though), the idea being to put as many walls between your students and the outside as possible. Closing the classroom doors when you moved into the halls was probably a good idea, since that more or less "completes" the additional wall that borders the hallway and would serve as an additional buffer to help stop any objects that blow in through the outside walls or windows.