I think you should listen to your mother, lol.
Seriously, I think 11 might be a little young in general, to have everything dumped on their laps. I think it is a good age to start, though, especially for girls who have menstruation coming up shortly. There are kids that might be able to handle all of the information. Every kid is different. It would depend on their maturity level.
Depending on age and maturity level, would probably expect them to either be grossed out, be bored, or to start experimenting earlier than they might have otherwise. And I wouldn't expect them to necessarily be responsible about it. Young ones, even teens, often have this sense of invincibility. They don't always think before they act, and do risky things. I educate my kids about sex and give them rules and curfews. They know it isn't a green light, so to speak. Just like I educate my kids about guns, and then I lock them in a safe. (the guns, not the kids
)