Jack Rimmer (portrayed by Jason Merrells) was headmaster at Waterloo Road Comprehensive School. He took the job when his predecessor was sectioned as 'mentally unstable'. He had a lax attitiude towards the school and initially let the students run their course. Later though, he joined forces with his deputy headmaster and began to restore the school to order.
After being instated as headmaster, Jack hires Andrew Treneman as deputy headmaster over a drink at the local pub. He is shocked to find Andrew’s crackdown regime and finds it completely out of order. The stress of two police incidents gets him very angry at Andrew but he nonetheless agrees to make a clear announcement to the school banning any assault on members of staff after separating student Donte Charles’ father, Clarence Charles from a fight with Andrew. The following Saturday he attends the wedding of Tom Clarkson and Lorna Dickey, both his employees and dances with an Steph Haydock, also an employee. His high spirits do not last long however as he receives word that the school has been broken into. He leaves the reception early with Andrew to find the hall trashed. He finally begins to consider the crackdown policy but insists on another visit to the pub first.
Jack calls Clarence into his office to discuss the car accident and grudgingly accepts to allow Donte to stay. Jack’s memorial service for deceased pupil, Adam Deardon, is thrown into chaos when his sister, Yasmin Deardon, throws an upset fit. Following the dance at the wedding, Steph asks Jack to go to a restaurant with her and he grudgingly obliges. Jack sees Donte into a police car and excludes Hadley Flynn for carrying a knife. At the restaurant, Jack feels very awkward as Steph flirts with him and tells him her life story. He tells her he is going to the lavatory but in fact heads to the bar. He then goes to the toilet where Steph is flirting with someone she thinks is him. He goes into a cubicle and pulls her inside.
Jack is disapproving of Andrew’s latest idea, a house system, but goes along with it all the same and tells student Lewis Seddon that he will give money to the winning house. When Steph brings student Chlo Grainger to his office, he calls for her mother and his employee, Izzie Redpath. After head of pastoral care, Kim Campbell, has trouble with a new pregnant girl, Zoe Ramsden, he calls the latter into his office and she tells him he is the father of her child, blackmailing him for £10,000. Drinking more and more alcohol and getting stressed, Jack is confronted by Tom who hands in his notice of resignation. Jack soon tells Andew of the situation with Zoe. He is lost for what to do and tries to convince Andrew he would not touch an underage girl, completely in vain. He then goes to Zoe and tells her he will not pay the money. He tells the staff of the possible incident and his imminent resignation and Steph that he does not want to date her. Jack is just packing up at the end of the day when Andrew meets him in the car park and tells him that Zoe has just given birth and that ex-pupil, CraigHarris is the father. Jack approaches Craig and hits him while Andrew claims he didn’t see the incident. (He did.)