I assume that 10/11 year olds have already had some exposure to sex education, Agent, and I would find it odd if parents with children of this age hadn't spoken to their dcs about puberty and sex and relationships in general, and more specifically periods and wet dreams etc.
I don't consider this is 'putting ideas into their head' - much younger children play 'doctors & nurses' and and are aware of the difference between the sexes, and other more 'adult' stuff whether by osmosis or idle playground chatter.
IME, parenting is an ongoing process, and parental knowledge (and hopefully wisdom) is imparted on an age-appropriate and need-to-know basis throughout childhood and beyond.
I was raised by liberal parents who took the view that the less they gave their dcs to rebel against, the less likely they would raise discontented or maladjusted adults.
Anything and everything was (and still is) up for discussion in my parents' house; rules of debate are strictly observed and, although conversations can get heated on occasion, no shouting is allowed.
Respect for the voice of the child is what underpins their credo and, as it worked for them and for me and my siblings, I've carried on the tradition.
Please note that this is not about parents attempting to turn their children into their 'best friends'!!! The parent/adult child relationship is not about 'equals', but it can be extended to 'equal entitlement'.
IMO at some point we have to trust our dcs to plot their path in life as much as they've trusted us to guide them. Of course we may feel some anxiety when our fledgelings are out of our sight, but if we have done our work well any anxiety should be misplaced.