Teachers with firearms could present a danger towards the children

They aren't trained professionals like an armed guard would be, where they receive almost daily training. If a teacher were to improperly secure their firearm, a child could gain access to it and mistake it for a toy, which could lead to an accidental shooting. As well as that, teachers mental health vary, and they would need to go through multiple tests and background checks to be eligible, if one of these checks were failed and a teacher got past it, they could end up being the suspect in a shooting.