Window configuration varied, still does, and sometimes bedroom windows were two together, radiator underneath both; other times they were the way you described the to be.
I had a bedroom with the double windows and the third window had an airconditioner in it, so there were many variables and still are.
Small children can and often do rather strange things with object...swallow something they shouldn't even have in their mouth, or, as your son did, when little, stick something strange up a nostril.
I take it that your son is now okay and never did something like that again!
Much of the lead-ingesting cases and resulting mental capacity damage has been done in low-rent/ownership tenement row-houses in the inner cities.
The children were allowed to crawl around the place unsupervised and when they could stand, the first place they where they could reach was the windowsill.
The blame for this was mainly on lousy, don’t care landlords, unattentive or neglect parents/siblings, and just the aging of the paint.
Also the use of cheap paints in rental units and projects.
Enough blame to go around the block, sadly.