The actress's feisty character will arrive at Waterloo Road Comprehensive later this year to investigate its progress following previous problems.
Speaking of how the newcomer causes a stir, a show source told The Mirror: "Her arrival couldn't come at a worse time. There is trouble between the staff and pupils - and she will come across it."
Asher is thought to be currently staying in Manchester while she films her part in the programme, which is set in Rochdale.
A BBC spokesperson confirmed to Digital Spy that Asher is guest starring in one episode.
As previously announced, new signings for the show's return include Scottish actor Alec Newman as the school's latest headteacher Michael Byrne, Jaye Jacobs and Alex Walkinshaw as married teachers Sian and Jez Diamond, and former Cold Feet star John Thomson, who will appear as a parent in regular guest appearances throughout the series.
Meanwhile, Chris Geere has signed up to make a comeback as ex-Waterloo Road teacher Matt Wilding, who is recruited to reinvigorate the music and drama departments.
Waterloo Road returns to screens in the autumn.
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