Qualified? In what? He is not very articulate.
A firearms expert is not the same as a physical security specialist who can do a full threat model on the pros/cons of arming teachers. The assumptions are “bad” primarily because they are overly optimistic. I have yet to read an pro gun analysis that states any downsides to this method proposed. They do not state any downsides at all. That gives me pause, it demonstrates lack of real physical security expertise.
Do these schools even have basic security reviews, district level security practices, crisis training, surveillance, lock down procedures, egress planning?
That all requires funding from tax payers. Is Gov. Abott going to fund that across Texas?
The strategy seems to be arm teachers (conceal carry)and shooter will either get killed or avoid the situation entirely. It is hard to know what a enraged psycho will do. You have to plan for it.
Read the play by play for the Ulvade shooting. The shooter entered from an unsecured backdoor and barricaded himself in the classroom. It was a surprise attack in an enclosed space with tens of children. Total chaos. The teacher(s) most likely would not have time to respond even with training. Even safety officers (with training and arms) have been known to flee (see Parkland shooting). This has to factor into the analysis.
Once you are in a hostage situation the stakes are extreme and school teachers are not really prepared to deal with that. Two trained police officers were shot in the situation, there is no real hope for a teacher with a few hours on the shooting range. What are the ages of these random teachers, capabilities, fitness, etc? It is a total tossup. The assailant was just one 18 year old, what if there are two or more (see Columbine).
These simplistic solutions fall apart on quick review.