I don't know that I want to say you are being a jerk. But I don't believe it's offensive for a business owner of any kind of business to set their policies. You should have known going into this that they charge for a flat weekly/monthly rate.
I've been providing care for 25 years and I so deserve a vacation. Somehow I keep thinking that one day I'll have a group of parents that are doing well enough that I can ask for one. But every one of my parents is struggling with something be it unemployment at times, under-employment, working 2 jobs, going to school and working full-time, no help from the fathers of the children, and those are just to name a few of the problems I hear about everyday.
I can't speak for that school you are using. But I bust my hump daily to provide the clean home, healthy food, up to date toys, equipment, and computers, AND provide good old fashioned morals, care, on time diaper changes, etc. My parents take vacations and many of them bring their kids to me during those vacations because they feel entirely entitled since they paid for it. I'm not here to take advantage of them. But I certainly would hope that they aren't bad mouthing me about the fact that I charge a FLAT weekly rate no matter what their attendance level is.