They never seem to have friends over or go to friends houses either do they?
Could be a few reasons
A. Bav hates all the other school parents still after last summers photo
B. Bav thinks she's too good for all the other school parents and her 'kiddos' are too good for the other children
C. The other parents dislike Bav so much they dissuade their kids from socialising with them outside school. (May also be afraid of her trying to rope them into PTA activities)
D. After last summers photo Chris did wait at the school gates like Bav promised, confronted some parents and alienated everyone
E. The Bavs are too tight to feed an extra child for dinner every now and then (fags to be bought etc). She doesn't feed her own kids a hot meal on school days.
F. Do you remember when you were young that house you weren't allowed in because your mum said they were dirty?...
G. All of the above?