When I was in the last year at primary school (1971-72), girls and boys were separated one afternoon.
While the boys were taken outside to do sport, we girls were given a lesson that was clearly meant to prepare us for periods.
I don't remember much about it, but it must have done the job, because I was not taken unawares when my periods started a year later.
Just as well, as my mother never raised the subject, though when I (reluctantly) had to tell her that they had begun, she produced a packet of sanitary towels for me to use, and explained that I might get headaches or stomach ache.
From then on, instead of 'pocket money', I was given a weekly allowance, out of which I would have to buy my own sanitary wear, amongst other things.
That was it. The subject was never mentioned again and I struggled in silence with my dreadfully heavy and frequent periods.
The only thing I do recall from that afternoon in primary school was being shown a film of a woman giving birth. I know that some parents were furious about their 'little girls' being shown such a thing.
My own dgd is only nine, but she has been well prepared by her mum for what to expect, and I know she is comfortable asking her mum about such things. Lucky girl 