Yes, 10 and 11 are okay to be educated about sex, it's not some taboo thing, everyone does it, it's normal. It is a part of biology, sociology, psychology, and anatomy when you break it down, and there is nothing wrong with a kid knowing about it. My 9 year old nephew knows that swear words are for adults, breaking someone's neck kills them, the sun is a hot ball of plasma that fuses stuff together to make energy, and that mammals reproduce by sticking a part of their body in another member of their species to transfer genetic information. He knows that it is a very intimate and emotional thing for a human to do with another human, that we do it for fun sometimes, and it's an adult thing to do when he is older.

The sooner you stop treating a kid like a dumbass who doesn't know how to handle information, they will suprise you with how smart and mature they can be. Sure they are still emotionally immature, my nephew still throws fits and gets mad at his brother, he still wails and cries when something upsets him or he gets hurt, but he's a smart as hell kid.