If you've never heard of it, the similarities between Harry potter and The Worst Witch are too many to be coincidence.

"I am sure that Jill Murphy's The Worst Witch is actually the roots of Harry Potter, even though J.K. Rowling has never admitted that. There are simply too many similarities between both worlds for it to be a coincidence, and if Murphy never sued I guess that it's because she did not want to suffer all the hassle.

Just consider these unusual coincidences:

1- Miss Cackle's Academy for Witches is a lonely castle, surrounded by forest.
2- The castle is invisible to non-magical people.
3- There is a village nearby the castle.

4- The forest is forbidden to the students.
5- Mildred Hubble comes from a non-magical background.
6- Mildred has two best friends, Maud and Enid.

7- Mildred has a cat.
8- Miss Hardbroom (scary potions teacher) hates Mildred.
9- Elitist fellow student from an elitist family of Witches hates Mildred.

10- Benevolent, warm-hearted Headmistress loves and helps Mildred.
11- The first year students take special lessons to learn to fly with broomsticks.
12- Miss Cackle's Academy was founded by a witch called Hermione Cackle.

All of these sound familiar, right? There are other similarities, these are just a few!!

Now, if Harry Potter had come first then everyone would scream that The Worst Witch is a Harry Potter rip-off, but in fact the first Mildred Hubble book was written back in 1974... J.K. Rowling is a wonderful writer and a superb storyteller and there are also many differences between WW and HP, but I think that all HP fans (myself included) should accept that WW is actually the roots."

https://mythicscribes.com/community/threads/the-worst-witch-tv-series.10979/post-153303