The Patriarchy of the Wizards

The wizarding world is rule by men for men. Surprisedly since there are around six times more witches then wizards, but with the right spells, oaths, potions and laws. Well women have very little to no say. So at the top are the pure blood males, who have harems of women. Pure blood women are at least treat with some level of respect, they valuable property after all. Half blood women are given mix treat, depending on their family and who owns them. They can expect some level of respect. Muggle born are basically slaves, even muggle born males can treat them like pets and no one cares. Unless they're own by a half blood or pure blood.

Muggle born males are told pretty early about this. Muggle born women aren't told at all and find out pretty quickly what they are. Since muggle borns aren't allow in until their eighteen years old. This is done to keep muggles parents from complaining and getting their law enforcement involve. There are laws to protect underage pure bloods, half bloods and muggle born until their eighteen birthday. That's why many half bloods and pure bloods have arrange marriages. To at least put some protection for their daughters.

All magical schools start at eighteen as well.