As someone who has raised two children in the US, I can tell you it is definitely not easy, nor is there a straightforward approach because each child is different and personal circumstances vary. However, we should certainly shield our children from being exposed to things that are inappropriate (vulgarity). As far as them learning about sex, although it is a normal human process, not every child has the maturity to understand or process it. Islam does not prohibit the learning of these things for a child that is baligh as long as it is appropriately done. Thus, my personal view is that a parent has to see the capacity of their child to learn and understand and then determine the right time. Moreover, (my feeling ) we should be careful not to over-protect our children because they will be exposed to these things no matter how hard we try to stop it. So, it’s better they see and learn under our guidance than outside of it.