Granny power is the often unrecognised mystery ingredient that makes or breaks a school. I made this amazing discovery during the annual school photograph day. I wanted to boost our school kitty - the commission on these photographs is a nice little earner - so after a few words with John, our photographer, I sent a letter home saying we would be happy to extend our picture arrangements to big brothers and sisters, babies, granny and granddad - even pets.

On the day, a Yorkshire terrier turned up for a family portrait, complete with pink bow and hair brush. We had a Rottweiler with studded collar and tattooed owner. But what really blew my mind was the number of grannies, grandpas, aunts and uncles. The granddads looked splendid with hair slicked into place, in best suits and teeth. And we thought Wayne’s Auntie Sandra had done us proud posing in an evening gown - although it turned out to be a long nightie. But it was a great morning and we made a bob or two.

The whole event got me thinking. It began to sink in that our school newsletters weren’t just for mums and dads. All the family clearly read them to keep up with what was going on. I began to reflect on who brought the kids to school and collected them - and I realised there was a high proportion of grandparents in our playground.

In a school serving a well-established community, and with mums and dads working, it falls on grandparents to look after the kids and get them to and from school. What were they saying? What were they thinking? Did they have a marginal or central role in opinion-making about the school?

A large number of grannies regularly attended the mums’ and toddlers’ group, so I joined them to find out what was going on. The grannies led the discussion on secondary schooling in the area. They made judgments and insightful comments; they knew about the kids who got good jobs or went to college, they knew about those who got into trouble or were permanently excluded, they knew about bullying.

They were also generous in their comments about staff who gave freely of their time, who were approachable and had the interests of the children at heart. They were fairly dismissive of governing bodies, including parent governors.

When I asked for their views on our school, they compared what we did with the schools that other grandchildren who lived out of the area attended. They commented candidly and at length about the standards of reading and maths - knowledge gleaned not from SATs results or league tables but from first-hand observation of listening to children read and count and watching them write. They had views on midday supervision and school trips and clubs - and they were astute and outspoken in their judgments about long-serving teachers.

They commented on the quality of report writing and were scathing of reports built around data banks. They said the reports could be about anyone; that there was nothing special to make it only about their grandchild.

Our appeals for parents to help in classrooms had always met with mixed success. So I began to target grandparents instead, as many had the time, skills and interest to make a strong contribution. For a time the parents’ association was managed and led by grandparents; they organised the school’s float in the local carnival, weekly bingo sessions and the summer and Christmas fairs.

Perhaps it might be time to think about a new name and a new slant for your parents’ newsletter. “Family newsletter” would be a good start.

Mike Sullivan is an education consultant and a former primary head. He is based in the West Midlands