They objected to her enforcing the school uniform policy which meant their 11-year-old daughter was banned from wearing a nose stud.
In response, the school tightened its security but, five years on, there is now a parent partnership policy at Francis Combe, a comprehensive in Watford.
Geoff Carr, deputy head, says: "We've opened ourselves up more to them, we're saying, 'We want to listen to you and hear your voice'. We've relaunched our parent-teacher association, and told them it's not about jumble sales.
"We want them to be an influential voice in the management and shape of the school. We want to evaluate the school day to see how we can improve teaching and learning. They are much more likely to help make it work if they are involved."