Digging around looking for a copy of Knowledge to use as an illustration for the entry below -- and the lack of one will tell you how successful I was -- I came across a copy of another children's educational magazine, How and Why, published by City Magazines.
Two things of interest. One was that How and Why reprinted material from the How and Why Wonder Book series originally published by Grosset & Dunlap in America in the early 1960s which, presumably, is where its title came from. I remember them being incredibly popular when I was a kid. These were intermixed with short articles which appear to be originals.
But what caught my eye was the name of the author of the first of these short articles entitled 'The Wall that Contained an Empire', about Hadrian's Wall. It's Hermione Grainger. Being a bit of a latecomer to Harry Potter (I've just finished reading Prisoner of Azkaban) the name kind of leapt off the page.
How and Why is undated, but was published in around 1963/64, running for 13 issues before the high price (2/-) killed it. Since J. K. Rowling wasn't born until 1965, she obviously didn't see the magazine first time round (unless she's got one of those little sparkly hour-glass pendants) but maybe she saw copies later and the name stuck in the back of her mind. More likely it's just a coincidence.
(* Yes, I appreciate that the Harry Potter character is Hermione Granger, not Grainger, but it's a curious coincidence none the less. A very quick dig around doesn't turn up anything else under the byline Hermione Grainger. If anyone out there spots anything by her, send me an owl.)