Mildred arrives for her second year at Cackle's in a positive mood. There's a new intake of young would-be witches one of whom, Sybil Hallow, is afraid of everyone including Mildred! In an attempt to be kind to Sybil, Mildred only seems to make matters worse. Meanwhile, an argument is going on in the staff room between Miss Bat and Miss Drill about who is to be the second year class mistress!

The girls are learning finger sparks to enhance the effect of Spells with Miss Hardbroom. Ethel delicately zaps away one pine cone, while Mildred puts a hole in the cupboard door. Not all the Hallows are at the top of the class though, as Sybil fails her broomstick flying test. Mildred tries to make her feel more comfortable, but for some reason, she always seems to say the wrong thing.

Ethel thinks it's Mildred's fault that Sybil is always following her around, so when things go too far during a lesson of broomstick flying, Ethel vows to get her back, by turning her into a frog! With the help of a wizard who has also been turned into a frog, Mildred just might turn back & figure out who did this to her!

Chief Wizard Hellibore is to give a master class in magic to the girls of Cackle's Academy. This is an ideal opportunity for Mildred to enlist his help to change her newfound frog friend back to his old self. Unfortunately, Mildred has been banished to her room and, as punishment, forbidden to attend the master class!

Panic spreads amongst the teachers when they're paid a visit from the Witch School Inspector. The particular individual appointed to inspect Cackle's Academy is none other than Mistress Broomhead, Miss Hardbroom's tyrannical personal tutor from witch training college. An emergency plan of action is drawn up and, in order to prevent any unforeseen disasters, Mildred is banished to her room.

There's a blizzard raging outside & the girls are desperately trying to stay warm. Amidst all the chaos, who should arrive seeking shelter from the weather, but Chief Wizard Hellibore, who is in a particularly mischievous mood & pronounces the day to be an upside-down day. Everything is turned on its head; teachers and pupils change places and there are games instead of lessons!

Mildred & her friends set off to visit Algernon at his riverside retreat. Mildred has been told to leave her cat behind, but when no one is looking she manages to sneak him in, hiding him on a boat. Meanwhile, Ethel and Drusilla discover the boat with Tabby & they untie the boat sending it down the river towards the rapids, completely unaware that Miss Hardbroom is also on board!

Ethel & Drusilla's prank casting a boat adrift with Mildred's cat aboard takes a dangerous turn when the cat & an unconscious, Miss Hardbroom head towards the rapids! Meanwhile, Merlin has accidentally frees a Dragon Lord from his captivity who threatens to imprison the town forever unless he gets his lost treasure back! Now its up to Mildred to save the day!

The first years are left with Miss Bat and Miss Drill while the rest of the school is away on a trip. The two teachers see this as an opportunity to put all their favorite educational ideas into practice. As a result, there's a lot of P.E. and chanting for the girls. In the staff room, Miss Drill and Miss Bat are competing for Miss Cackle's vacant chair and the authority it confirms.

Frank's nephew Charlie has arrived for a visit to Cackles. He's fed up with his own school and jealous of the fun the girls seem to have at the Academy, so he persuades his uncle to ask if he can become a pupil at the Academy. Miss Drill seems sympathetic to the request but Miss Hardbroom is dead set against it. Leaving Miss Cackle wondering if it might not be time for the Academy to go coed.

The girls are restless, & they can't wait for the term to end. Miss Drill introduces the girls to basketball and arranges a friendly match with the Hevversham Hevvies! The Hevvies are ruthless & walk all over the girls. Mildred is hopeless and has a tendency to freeze when it's time to shoot at the basket! The entire school is watching, which doesn't make it any easier for her!

Mildred's potion exam, & gardening competition are both happening at the same time! Her chances of passing look slim, as Ethel and Drusilla conspire to get her thrown out of Cackle's. When Mr. Blossom's greenhouse is trashed, Miss Hardbroom suspects Mildred, & forbids her from participating further.

The girls are very excited because it's the thousandth birthday of the Castle! Miss Bat is preparing a performance of the Spell girls with Fenella, Griselda, Sybil and Clarice. While Mildred is elbowed out of her drama slot by Ethel! Meanwhile the girls are shocked to find that Ethel's father & the Chair of the School, is planning to sell the Castle!