Some contracts include the right for the employer to vary the contract unilaterally. In Hart v St Mary’s School (Colchester) Ltd, the Employment Appeal Tribunal (EAT) held that a variation clause in a teacher’s contract was not clear enough to allow the school to change the terms of her contract unilaterally.

Basic facts

Ms Hart, a part time teacher at the school since 2001, worked Tuesdays, Wednesdays and Thursdays every week. In 2013 the school decided to change the timetable so that certain core subjects could be taught in the morning. As a result, the school required Ms Hart to spread her working hours over five days instead of three.

Clause 1.4 of her contract stated that: “In the case of the Teacher on a part-time contract the fractional part will be notified separately and may be subject to variation depending upon the requirements of the School Timetable.”

Clause 2.1 stated that during term time, teachers must work all school hours while the school is in session and at any other time “as may be necessary in the reasonable opinion of the Principal for the proper performance of his/her duties.”

Following Ms Hart’s refusal to agree to the change, the school implemented it unilaterally with effect from 1 September 2013. She resigned two days later and claimed constructive dismissal. Her resignation letter referred to the employer imposing a five-day timetable and also mentioned her caring responsibilities.

Tribunal decision

The employment tribunal judge rejected the claim on the basis that it was not custom and practice for Ms Hart to work three days per week. The school had a right to vary her contractual hours, it had consulted with Ms Hart in good time, provided her with the business document explaining the changes and allowed her time to put forward proposals. The judge concluded that there had not been a breach of a fundamental term in Ms Hart’s contract that entitled her to resign in response to it.

In any event, the judge held that Ms Hart did not resign in response to a repudiatory breach of contract as her letter of resignation indicated that she was resigning in order to continue with her caring responsibilities at home. Alternatively it was because of ill health, the reason she gave in evidence to the tribunal.

EAT decision

The EAT agreed that the wording “may be subject to variation depending upon the requirements of the School Timetable” was unclear. On the one hand, it could mean that the variation was more likely to be at the school’s request, but equally, it could be at the request of the part-time teacher. Both variations would have to be subject to the requirements of the school timetable. The school could refuse a teacher’s request for a variation and vice versa. Even though the requirements of the school timetable might suggest to the employer that there should be a variation, it did not, in the view of the EAT, amount to a power to vary unilaterally.

Secondly the tribunal judge had failed to ask whether the purported variation could have been part of the reason for Ms Hart’s resignation. The EAT described the judge’s reading of the resignation letter as “very strained” and concluded that, on a proper reading, it was arguable that the variation was at least part of the reason for the resignation. As the law did not require “sole causation or predominant effect”, this was sufficient for the repudiatory breach to be part of the reason for her resignation.

The EAT substituted a finding that there had been a repudiatory breach of contract and sent the matter back to a fresh tribunal, to consider whether there had been a constructive dismissal.


This judgment serves as a reminder to employers that, usually, contracts can only be varied by agreement. An employer will only be able to rely on a clause which gives the employer a unilateral right to vary, if the clause is in very clear language.