(This was a response to another person’s Medium post about porn.)
Some statistics indicate that kids are first being exposed to porn around 10–11, and I’ve worked with a number of couples where the guys especially have only learned about sex from porn and need to be re-educated.
Here are some more free resources:
Make Love Not Porn — devoted to portraying real sex and diversity, and debunking myths propagated by porn.
Pornhub has created a Sexual Wellness Center on their website, as well as a bunch of instructional videos like this one (you may be shown an ad for the porn site first which you can dismiss if you like).