Mrs Armstrong, who won the Local Authority Caterers Association award last month, made her children, Katie, 20, James, 15, and Jane, 13, eat her tomato and chilli pasta dish every night for a week until she got it just right.
The 42-year-old catering manager at Caedmon school, in Whitby, North Yorkshire, said: "I try it on them, because they always tell me the truth.
But in the end, they were sick of it and would say, 'Oh no, not again'."
The dish, dubbed Captain Cook's pasta, which impressed Ready Steady Cook chef and competition judge Brian Turner, will be one of the 15 recipes Mrs Armstrong reveals as part of the Get Active campaign.
Each week a new recipe will appear on the Get Active website.
Healthy eating is key for the 560 pupils, aged 11 to 14, at Caedmon, and the message is hammered home at every opportunity. Fizzy drinks, with the exception of Lucozade, are banned: the drinks machine only stocks water.
Sue Rowland, a languages teacher, even gets Year 9 pupils to keep a food diary in German and French.
Mrs Armstrong, however, does not take any chances and secretly grates fresh vegetables into the food she serves the children.
She said: "The children don't know this, but we sneak grated vegetables into the shepherd's pie and curries. It gives them that little bit of extra nutrition, and they can't say they don't like it because they're eating it without knowing."
The self-taught cook's other secret weapon is giving her oven-baked dishes a sporting twist. At the time of the World Cup, for instance, "Korma with a Kick" and "World Cup Whirls" appeared on the menu.
Mrs Armstrong, a season ticket-holder for Middlesbrough, said: "I have one dish called Ravanelli's Ravioli - the head's a Newcastle supporter. We charge him double when they win."
Healthy foods can be encouraged by being presented in an attractive way, she believes. And a make-over on the salad counter has had good results.
She said: "Even though it's not a top restaurant, you want the children to look and think that it is really nice. I don't want them to think it is just a school dinner. It has got to be perfect."
Mrs Armstrong's dishes are also a hit with staff. Sarah Clancy, a science teacher and behaviour support worker at the school, said: "Her macaroni cheese is gorgeous. I love it. I was the first in the queue today."
James Landers, 13, agreed: "The macaroni cheese is top quality; it's better than my Mum's."
Patrick Nedley, 12, said: "I usually get sausage and chips. But when Sharon tells me to have jacket potato instead of chips I do as I'm told."