Is it legal for a school bus driver to overcrowd their bus?

My bus is ridiculously overcrowded. It's shared by a large group of primary school kids, slightly fewer middle school kids, and then about eight high school students, including myself. Today, all of the high school students that were there had to stand on the way home because of how many younger kids are on the bus. I'm not exaggerating. This situation has been getting worse and worse and now people have to stand every day. There's nothing for the people standing to hold onto... And there is a sign on the inside of the bus that says,"no standing permitted.". Is this legal? I know it's far from safe.