Sally Stewart is Imogen Stewart's mum.
In Series 8 Episode 4, for Imogen's birthday, Sally tried to get Imogen to show off her body by getting her heels and a showy dress. When she got a letter saying her ex-husband, Tony was getting remarried, she was devastated.
While dropping Imogen off at school, she decided she wanted to come in with her. While telling workers where to put the machines for Tariq's fundraiser, Michael Byrne showed up. She explained who she was and why she was there. She walked away, trying to find the toilets, when she asked Connor Mulgrew where they were. After he decided to show her, Sally asked what his name was and he told her. When she found out he was in the same year as Imogen, she asked if he knew her. He answered to the best of his abilities.
In Daniel Chalk's class, Connor told Imogen that he had met her mum, and she was too friendly. Imogen stormed out of class to the gym. Sally was exercising as a group of guys watched. Imogen stormed through them, yelling at her mum. Sally said she should invite Connor to the wedding with her. Imogen got angry and stormed off again. Imogen later found Sally with Gus Hancock, in bed together.
When Imogen was a kid, she had meningitis, making her almost completely deaf and in need of hearing aids. Sally blamed herself, because she missed all the signs. Sally also thought that people would treat Imogen differently if they knew she was almost completely deaf.
At the end of Series 8, when Christine Mulgrew became acting headteacher, Sally wanted to remove Imogen from Waterloo Road. Sally walked in to Christine's office, interrupting the conversation she was having with Nikki Boston. When she told Christine her plan on removing Imogen, Christine was furious when she found out she was the one who told Sally about Imogen and Connor's relationship.
In Series 9, Sally was on the panel interviewing Christine and Simon Lowsley for the permanent headteacher post, alongside Robert Bain.