Sabrina enrolls in secret witchcraft training classes while attending her normal high school, but discovers she must share her clandestine instruction and her regular school with Portia, a snooty young witch from the “other side”. Thus the stage is set for magical mayhem in the craziest, weirdest, most mixed-up world of all: high school.
Greendale Highschool is holding it's first dance and Sabrina can't wait to go. She hopes that Harvey will ask her out to the dance. Later that night Harvey calls her to ask her out but Sabrina is also on the other line talking to her best friend Maritza. Unfortunately Sabrina mixes up her call-waiting and rejects Harvey's invitation by accident. After this Cassandra tries to ask Harvey out to make Sabrina look like a fool, but Maritza overhears Cassandra's wicked plan and asks Harvey out herself. Sabrina then sees this and ends her friendship with Maritza. Cassandra then convinces Sabrina to help her create a spell to teach Maritza a lesson. At the dance just when they are about to use the spell to get revenge on Maritza, Sabrina discovers what really happened. She apologizes to her and then uses the spell on Cassandra instead.
Cassandra is the best at everything at both Greendale High School and at the Witch Academy. She often taunts Sabrina about her victories but when a school fundfraiser begins Sabrina decides to prove she is the best at that by selling the most school cookies. Cassandra also sells cookies for the school fundraiser and casts a spell on Sabrina's cookies to taste horrible and ruin things for her. Thanks to some help from Salem Sabrina finally sells all her cookies and gets rid of the spell Cassandra placed on the cookies. Sabrina earns enough money for the school, beating Casandra and proving that she is the best at something.
Sabrina, tired of Harvey being too busy to hang out, casts a spell that makes the boy overly obsessed. He even follows her to the Witch Academy, placing her in detention. She then casts antoher spell which makes him overly obsessed with himself. She has to reverse the spell before his baby pictures in the school paper go out.
After putting off her history report until the last day, Sabrina conjures up Attila the Hun for refrences. In order not to be outdone, Cassandra conjures up Gengus Kahn, and the two barbarian warriors then set out to conqure the modern world together.
When spiteful Cassandra starts to spread harmful rumors, Sabrina goes to the rumor mill in the Netherworld to starts some rumors about her, but she only frees some monsters who are gossip incarnate that try to take over Greendale.
Sabrina accidently creates a monster worn that feeds off jealousy, and gets bigger.
After Sabrina's hair gets messed up after swimming she decides to use a spell to create a shampoo to have perfect hair. The spell works and will always keep her hair perfect, but under one condition. She can't ever have water touch her hair or body. So Sabrina decides to go without bathing to keep her hair perfect. Everyone at Greendale Highschool admires her hair, but Cassandra doesen't and she decides to steal Sabrina's magic shampoo and give it out to her popular mortal friends to use. Unfortunately instead of giving them good hair it turns them into werewolves and it's up to Sabrina and Cassandra to break the spell.
In spite of having the flu, Sabrina sneaks off to a witches' charity ball and infects the entire Netherworld.
After a very bad day at school, Sabrina goes to the Netherworld to get her broom updated, but she spends her credits going to the Dreamworld instead while neglecting her responsibilities and her life in the real world.
Sabrina thinks that she can coast through her history of warlocks class with Salem as her teacher, but he refuses to go easy on her when she neglects her studies.
Sabrina conjures up an adorable pet but Salem discovers that she has actually discovered an evil warlock who is trying to drain her of her powers. Unfortunately, Sabrina does not believe Salem which leads to further complications.
While fighting over the leading role in the school play next to Harvey, Cassandra puts something in Sabrina's brew during cauldron class that makes it an invisiblity potion. The girls use the potion to get back at each other until it cause only parts of them to become invisible, and they have to go to the middle of nowhere in the Netherworld or fade away to nothingness.
Sabrina casts a spell causing a teacher to fall in love with Mr Snipe. When she realises the feelings are not reciprocated, she tries to reverse the spell, but instead makes all the other teachers at Magic School fall for Mr Snipe. Eventually, which the help of Enchantra Mr Snipe forgives Sabrina and she is able to return things to normal.
Sabrina and Cassandra create magical doubles of themselves so they are able to go to a party while their doubles stay for avolleyball practice. The doubles, however, are the exact opposites of the real Cassandra and Sabrina. The former is sweet and nice, but the latter is a mean and nasty girl who causes no end of trouble.
Sabrina and Cassandra are chosen to represent Greendale High School as a team in a witchcraft contest, but instead of working as a team, they try to best each other. Sabrina uses a forbidden spell she learned from her aunts to accidently fused first them and then herself and Cassandra together in one body.
Both Sabrina and Cassandra turn their pets into dogs in order to compete against each other at the Greendale Dog Show.
When Salem accidentally shrinks her clothes in the wash, Sabrina gets worried that she is putting on weight, and she goes on a starvation diet to be thin enough for School Picture Day.
Sabrina plans to hold a party while her aunts are away, but they give her a baby-sitter, so she casts a spell on the sitter in hopes of making her a teenager for the party, but it only turns her into a baby.
Sabrina takes what she thinks is a rock from the Netherworld, but it turns out to be an egg which hatches into a baby dragon that steals Cassandra's necklace, and Martiza gets blamed for it.
Sabrina and Cassandra try to forget their differences as they search the Netherworld for a rare herb.
When she thinks that Cassandra is cheating to win a TV talent show, Sabrina uses a spell to improve her chances, but it only removes rules and ethics from the world.
When Sabrina promises a friend that she would go to a rock concert with her and her aunts that she would go to a Netherworld spa with them on the same day, she buys a magic watch that can turn back time so that she can do both. Using the watch too often, however, ages her, and she becomes an old woman overnight.
A magic mirror sends Sabrina and Cassandra to an alternate universe where not only do they loss their powers, but all the mortals their are witches and warlocks, and all the witches are mortals and treated like dirt.
Salem finds out that an evil warlock named Toc-Toc has been released from 75 years of suspeneded animation, being blamed for a crime Salem committed, and is out for revenge on him. Being the coward he is, he asks Sabrina to disguise him as a teenager and let him hide out at school. Unfortunately, Toc-Toc also changes into a teen and tracks Salem down. Salem has to own up to his mistakes and confront Toc-Toc.
Cassandra unwittingly helps a disgruntled witch take over the Netherworld by polluting it and turning all the witches there to stone.
The fairy Puck takes advantage of Sabrina and Cassaindra's bickering to become the star of the school's production of ""A Midsummer Night's Dream.""
