Paul,
I'm sure your basic premise is correct but the school board in Enterprise has a much bigger liability problem now. First, as Wayne pointed out, if the school knew the weather was predicted to be severe, why have the children in school in the first place? My NOAA radio went off at 0721 this morning with a tornado watch. It seems like an untenable solution to cancel school everytime there is a tornado watch - school would be cancelled about once a week during the spring.
Alabama schools constructed since about 1960 have all included areas that are structurally able to withstand most tornado damage. I'm making what is perhaps a rash assumption that Enterprise High School had such a safe area. If the children had been sent to a safe area, there probably wouldn't have been any deaths (which are now being reported as 5 rather than 15 - there seemed to be some real scene coordination problems there). From news reports, the children were sent to the gym to wait for busses because it was raining. I'm no structural engineer but I know that the worse place you can be in a high wind event is in a structure with a large, minimally supported roof. As soon as the wind gets under the roof, the walls lose their structural integrity and collapse. Apparently, this is what happened today.
The reasonable solution seems to be to keep the children in school and in a safe area if a tornado warning is given. Yes, there is some liability in doing this but it's hard to sue and win against a government agency for following a reasonable emergency plan. I'll bet that having kids standing around in the gym waiting for busses while there was a tornado warning in effect is not part of the emergency plan. This is where they are going to have legal problems.
Paul, you didn't get sent home from school because school officials knew that the school was safer than probably 95% of the homes in Alabama if it was hit by a tornado. They also knew that the probability of a direct hit on any one place, including a school, was small. If, in fact, there was a real danger of the school being in the path of a tornado, would any reasonable person think the right thing to do was load all the kids in school busses and hope they don't fly too far if they are hit? I spent 25 years in emergency management and I know that something went wrong at that high school. If it was fear of liability by keeping the kids in school, they not only increased their liability by trying to get them on busses but, more importantly, cost some children their lives.