Aside from the natural inclination of the school officials to want to prevent an ebola outbreak amongst the students and then the rest of the community, they are probably less fearful of one lawsuit than of a school-load of lawsuits if any other student caught the virus.
Are the parents liberal operatives or simply victimhood-seekers? How much trouble was it to have their child at home, presumably with schoolwork to do?
The point is, Nigeria is not an Ebola plague area. Liberia is, and the names are similar.