My kids (7 and 8.5 years old) were swimming during...

My kids (7 and 8.5 years old) were swimming during the free swimming time today while their grandfather was sitting outside of the pool watching them through the facility window. Shortly after they swam for several laps, my kids were asked to get out of the pool because they're under 10. Person in charge there told them according to Law, children under 10 can only swim when the supervising adult is also in the water. I have never heard of such law before because my kids have been swimming in YMCA while I was watching them outside of the pool. When I was trying to ask questions about the law through phone, the person on the phone was very rude and refused to talk to me about it. So my kids had to left the pool. It was a very unpleasant experience of my kids and their grand father.