Planning permission was granted in 2020 for almost 100 homes on the plot.
This included the conversion of the former school into 27 apartments plus the construction of 22 houses and bungalows, and a two-storey block of 49 retirement flats at the other end of the site, with a landscaped open area in the middle.
Now, Northumberland Estates has submitted an application to modify the design to increase the number of retirement flats to 52.
A Northumberland Estates spokesperson said: “The amendments relate to minor improvements in design and materials, and it remains a high-quality development for the town.
"The old school is a listed building and has been vacant for a number of years, therefore the first stage of work will involve extensive repair to the roof alongside the commencement of the smaller mews style cottages, which are aimed toward retirement living.
"We expect to begin construction towards the end of the year.”
More than 60 objections were lodged to the original application, in large part because the Alnwick and Denwick Neighbourhood Plan designates the southern half of the site as ‘local green space’, where ‘development will not be permitted other than in very special circumstances’.
In his report, the planning officer concluded there were very special circumstances in this case, due to the proposals allowing the long-term use of the grade II-listed school buildings, the full replacement of the playing fields, the provision of flats for the elderly and affordable homes, and part of the site becoming accessible open space.