Bedknobs and Broomsticks

During The Blitz, the three Rawlins children, Charlie, Carrie, and Paul are evacuated from London to the remote village of Pepperinge Eye. They are placed in the reluctant care of Miss Eglantine Price, a reclusive woman who agrees to the arrangement temporarily. The children attempt to run back to London, but change their minds after observing Miss Price attempting to fly on a broomstick. Miss Price reveals she is learning witchcraft through a correspondence school with hopes of using her spells in the British war effort, and offers the children a transportation spell in exchange for their silence. Miss Price casts the spell on a knob that the youngest child, Paul, has removed from the bed in the childrenâs shared bedroom, and she adds that only Paul can work the spell.
Later, Miss Price receives a letter from her school announcing its closure, thus preventing her from learning the final spell. She convinces Paul to use the enchanted bed to return the group to London and locate the headmaster of the college, Professor Emilius Browne. They discover that Browne is actually a charismatic showman who created the course from an old book he found and is surprised to learn that the spells actually work for Miss Price. He gives the book to Miss Price, but she is distraught to discover the final spell is missing. The group travels to Portobello Road to locate the rest of the book. They are approached by the spiv Swinburne. He takes them to his employer, a mysterious man known as the Bookman who possesses the remainder of the book. They exchange their pieces, but they learn only that the spell was inscribed on a medallion, the Star of Astaroth, that belonged to a sorcerer of that name. The Bookman reveals that the medallion may have been taken by a pack of wild animals, given anthropomorphism by Astaroth, to a remote island called Naboombu.
The Bookman doesn't believe the island exists until Paul confirms its existence via a storybook he found at Mr. Browne's residence. The group fly on the bed and land in the islandâs lagoon. They are brought before King Leonidas, the hot-tempered lion who rules the island. Leonidas is wearing the Star of Astaroth. Leonidas invites Mr. Browne to act as a referee in a soccer match. The chaotic match ends in Leonidasâ self-proclaimed victory, but Mr. Browne cleverly swaps the medallion with his referee whistle as he leaves. Upon examining the Star, Miss Price finds the missing spell, âSubstitutiary Locomotionâ. When he discovers the theft, Leonidas pursues the travelers, but Miss Price transforms him into a rabbit and they escape.
Back home, Miss Price prepares to try out the spell, but the Star has vanished back into the fantasy world of Naboombu. Paul reveals that the spell "Substitutiary Locomotion" was actually in his storybook the whole time. Miss Price tries the spell on Mr. Browneâs shoes; while the spell works and imbues the shoes with life, she finds it difficult to control them. Mrs. Hobday, the local supervisor for the childrenâs refuge, informs Miss Price that the children can be relocated with another family, but Miss Price wants them to stay. Mr. Browne is leery of commitment, and when the children refer to him as a father figure, he returns to London.
A platoon of Nazi commandos land on the coast and invade Miss Priceâs house, imprisoning her and the children in the local museum. Mr. Browne comes to the rescue after observing more Nazis disabling phone lines, inspiring Miss Price to use "Substitutiary Locomotion" to enchant the museumâs exhibits into an army. The army of knights' armour and military uniforms chase the Nazis away, but not before they destroy Miss Priceâs workshop, ending her career as a witch. Though disappointed her career is over, she is happy she played a small part in the war effort. Mr. Browne enlists in the army and departs with the local Home Guard escorting him, while Paul reveals he still has the enchanted bedknob, hinting that they can continue on with their adventures.

Question: Where did Miss Price receive a letter from?
Answer: Her school