The deals are worth £80m in construction and facilities management revenue, according to Interserve, which said it would invest around £3m in the two projects.

The first contract, for St MacNissi's Educational Trust, covers three schools: St Joseph's primary school in Carryduff, St Mary's primary school in Portglenone and Our Lady and St Patrick's college in Knock.

The fourth school, St Patrick's grammar school in Downpatrick, will be built on behalf of the Trustees of the De La Salle Congregation and will cater for 665 secondary school pupils.

O'Hare & McGovern aims to build the schools over the next two years, after which Interserve will manage them for a period of 25 years.

"We are looking forward to delivering services to the local communities who will benefit from these new schools," said Adrian Ringrose, Interserve's Chief Executive.

"These are Interserve's sixth and seventh educational PPPs in Northern Ireland and, together with the Enniskillen Hospital project in the south-west of the province on which we reached financial close recently, they underline both the continuing importance of the PPP model as a means of delivering social infrastructure and our commitment to providing modern, effective facilities for the people of Northern Ireland."