With more than 60 years' service between them, Dot and Thelma are the epitome of loyalty, says chair of governors Daphne Price, who nominated them for our flowers, champagne and chocolates. She says they are hardworking gems whose pride in the cleanliness and appearance of the school goes way beyond the norm - they often clean the hall twice a day when there's an after-school function. And they're always cheerful - "no moans about mud in corridors, or rooms unavailable for meetings after hours".
Headteacher John Smith agrees Thelma and Dot are a fantastic asset to the school which, during their working lives, has evolved from a boys' secondary modern to a 900-strong mixed comprehensive for 11-18s.
In recent years Northgate has been awarded a gold Sportsmark, a silver Artsmark and a school achievement grant, which all the staff shared in.
He says Thelma and Dot always support school performances and are active fundraisers. Their brother is involved too - running country and western dances to raise money for the school's specialist status bid.
The sisters are part of two "super teams" of cleaners and kitchen staff, and they clearly relate well to the students. "They're very supportive to the youngsters," says Mr Smith. "They mother them and look after them and help everyone feel part of things. They're special."