well, presumably you have chosen to send your dd to private school, a choice which has been aided by funding received from elsewhere? You were after all not forced to send her - you could have sent her to state school if you had wished. It just happens that you are able to send your dd to private school through funding from others, so yes, you are privilaged to be able to do so.
As for parents paying on the overdraft, I personally wouldn't, but if the state schools nearby are failing parents may choose to do this to give their children the best education possible, or if they were previously able to afford it and then fell on harder times, it is perhaps the best they can do so as not to disrupt their children's education by moving them from a school where they are happy and have friends, to one where they'll have to start all over again.