I feel that he should be charged because his job is protection of the school and he failed miserably at it. He chose to stay safe while other officers ran inside when they arrived and dealt with the situation.
Too often I have seen where an officer can't hack the street and ends up as the SRO, that needs to stop. If a cop can't hack it, he needs to find a job he can hack. The problem we run into is that there is already a shortage of officers, and now more people might decide to find another profession. Makes for an interesting conundrum.