More horror than SF, but only horrifying in concept... I didn't really feel anything for the kids, but just knew that I should, if that makes sense.
It seemed like a metaphor for something, tbh. As if the alien girl represented adulthood, and the way she 'infected' the other kids was by instigating puberty in them or something. But not really, either.
I think that it was spoiled by the fact that the title and blurb gave too much away.