Too girly or too boyish. Too thin or too fat. Too quiet, too loud. Be ambitious, but don’t hurt feelings. Be inquisitive, but don’t interrupt. Be outspoken, but don’t be bossy. Most of all, be yourself—but be a lady.

What’s a girl to do in a world filled with contradicting gender expectations, aside from saying sorry?

The way we teach politeness norms to children is often confusing, changing based on gender—and can have lasting effects. And while everyone should be courteous and accountable for their actions, apologetic language out of...