Plans to move half the pupils in a senior school to a new site have been postponed for a year while building work is completed.

Half the 1,300 11 to 16 year-olds at Barnwell School in Stevenage were due to move to The Heathcote School site in September, but will now stay put until remodelling of the site is competed.

Heathcote will see its last pupils leave this summer after a decision by the local education authority, Herts County Council, in 2006 to close the school. Renovation and redevelopment of the site costing �4.6m is expected to begin in late summer to early autumn after funding was agreed by HCC last month.

The Barnwell u-turn was made by senior staff after reconsideration of the effect of building work on pupils.

A statement by acting headteachers Paul Barnett and Tony Fitzpatrick and chair of governors Julie Ashley-Wren said: “The best and least disruptive approach to carrying out these works is for them to take place before any students begin to occupy the Heathcote site.

“For this reason, during the academic year 2012 to 2013 Barnwell School will remain as a middle and upper school, with the upper school students remaining on the east campus for the entire academic year.”

In a further development, plans to keep Barnwell’s east campus as a purely sixth-form site with over 200 pupils are now in doubt, with a 50 per cent chance of closure, the school said.

A three campus model, incorporating the former Collenswood School site is dependent on securing a suitable education partner to co-locate there, but an application by Hertfordshire University to open a technical college on the site was rejected by the Department of Education.

The acting heads said: “This development gives us the opportunity to reconsider if a two or three campus model would be best to deliver the vision of Barnwell School. During the spring term the local authority will be assisting us with a feasibility study to see what would be the best way to restructure the school.”

The result of the study is expected by Easter.

If the east campus is closed, funding will be necessary for sixth-form buildings on the remaining sites, a spokesman for the school said.

Part of council’s �4.6m redevelopment funding of Heathcote will go towards a four classroom expansion of neighbouring special needs school, Greenside. Plans remain unchanged at the school to move into the new buildings upon completion.