bonsoir - I find your posts disturbing at best. You come across as very judgmental to about other peoples parenting. Why shouldnt children of opposite sexes play together, even in a bedroom. I have 3 DSs aged 3, 9 and 18 and Ive always let their friends, of both sexes into their rooms.
The only thing attitudes like yours wil ldo is make children grow up scared of the world - yes bad things can happen but parenting needs to be a careful balance between teaching children the dangers without naking them completely afraid - bad things dont happen to you know. As someone who works with people who have been abused I can tell you abuse happens outside of the bedroom and within the family to. It sounds like you see everyone as potential abusers - or are boys simply the victim of nasty girls out to ensare them with their bodies?? FFS mad.
"Put down firm and proper boundaries and nothing bad will happen." - absolute rubbish Im afraid, people have to learn the coping mechanisms to deal with "bad things" - whatever they may be or they will grow up into adults with no coping mechanisms and therefore make mental health problems more likely.