Charging full price is appropriate to encourage you to leave your child at home with a babysitter, where he or she belongs. There is no rational reason for a 1-year old child to ever be inside an operating movie theatre. The only thing they can do is distract or disturb other people from enjoying the entertainment. \r
Many thoughtless parents are so attached to their little darlings, they never even consider what an affront a fussy child is to other paying customers. Not to mention that the kid really doesn't want/need to be there anyway. Really, people, a little common sense goes a long, long way.