I'd never seen this and someone recommended it. I thought it was a bit long, but otherwise was well-done.
It's WWII and London kids are getting farmed out to rural areas so they won't get hurt. At this rural area, there's an apprentice witch, Eglantine (Angela Lansbury), and she gets stuck with three siblings. They have trouble at first, but then get together to go to London and get the last spell for her to be a real witch. She gives the youngest child a spell having to do with a bedknob that will fly the bed all over. It turns out the guy who was running the correspondance witch school was just an illusionist and was startled to find out Eglantine was a real witch. They need to find a phrase to make her finish her school -- they have an extended dancing series on Portabello Road and then a trip to an animated land of talking animals before they get back and find the phrase.
Just as she's trying to use it, they find out that German soldiers are in the rural area and are captured by them. They can't get out of the museum, but, hey, there's lots of armor and uniforms. Eglantine manages to make them move (one of the best works in the movie, I think), and they manage to kill or banish the German soldiers.