Yes, he did. You have to take a few things into account. Was the SRO in the same area as the shooting at the start?. First of all, it's gonna take a few seconds, at best, to figure out something's wrong. I don't know the layout of this school, but if it's like most - it's large with a lot of hallways..........where sound echoes around. It might have sounded like the shots were coming from another area. And even if the SRO does a fantastic job and in 10 seconds puts and end to it - think of the weapon this CHILD used...........it's made for war and it can do incredible damage in 10 seconds. That SRO probably did save a lot of lives the other day.
When the plane landed in the Hudson River, they had people in flight simulators try to determine if Sully could have made it to Teterboro airport. They said yes he could, because in their simulation as soon as the bird strike happened they turned the plane toward Teterboro and made it back. But what they didn't do is give the realistic time needed to figure out how badly the bird strike damaged the engine and if they could keep flying. I think Sullenberger and Jeff Skiles made their determination in about 40 seconds, which is actually pretty amazing and that 40 seconds made the difference. Maybe they could have made it to Teterboro, but that airport is surrounded by buildings and homes, they couldn't risk it. Gotta factor in time to asses.