Yes. Absolutely.
Those teachers who wish to be armed, and who go through training in tactics, etc, absolutely should be able to be armed.
Or, if a school district prefers, and can afford it, armed guards should be hired and stationed at or near access points to the school.
The silly notion that "we should not have to have armed guards at school" is simply ludicrous.
If we have armed guards at every OTHER location where "precious" items are located (banks, museums, sporting events ?) how silly is it to NOT have armed guards protecting our CHILDREN, for crying out loud?