Sounds like you're doing a good job to be asked back. Maybe the two girls enjoyed the afternoon because you kept certain individuals in line who would normally be disrupting the class? I wonder if quieter and more conscientious pupils get fed up with those who regularly cause problems and they therefore appreciate your firmer approach? I always think that if children like you it's a bonus, but it's more important that they respect you and behave well. Maybe try to avoid over-analysing what you hear from staff and pupils - although I know that's hard!