Woodlands primary has run its own five-term calendar for the past five years and was devastated when it had to switch to a six-term year this September along with its neighbouring schools.
The Grimsby school has seen its Sats scores soar since 1999 when 40 per cent of pupils achieved level 4 or better inEnglish key stage 2. This year it was 74 per cent.
Robert Beel, headteacher, said the system of five eight-week terms, with two-week holidays in between and four weeks for summer, was a logical one.
It helped prevent pupils getting too tired. He said: "We certainly feel the five-term year contributed greatly to the ethos and success of the school."
However, none of its neighbouring schools adopted the system and Woodlands agreed with North-east Lincolnshire council to adopt the six-term system with its neighbours once the five years was up.
Mr Beel believes the six-term calendar is not very different to the traditional three-term year.