Seven people, all believed to be parents, were arrested after a mass brawl outside a Birmingham primary school.
The fight took place at the gates of Firs Primary School in the Bromford area of the city on Wednesday morning.
All seven were arrested for violent disorder and later given police bail.
A West Midlands Police spokeswoman said the violence flared after another confrontation on Tuesday evening.
"As a result of the incident on the Tuesday, we put extra patrols on. While the police were patrolling, they came across a fight involving a number of people, believed to be parents," she added.
Birmingham Local Education Authority refused to comment further on the brawl, other than to confirm that an "incident" happened outside the school gates.
But teaching unions said they were concerned about increasing levels of violence among parents.
Brian Carter, the NUT's Midlands secretary, blamed the Government for its emphasis on parental rights rather than responsibilities.
He said: "It's important that parents behave in an appropriate way and set an example to their children otherwise teachers have a harder task.
"We must have good role models in our society but we look to parents to provide the best example of how to conduct themselves.
"This (the violence) adds to the burden of teachers trying to push against a drifting tide of increased lack of respect for schools and school communities.
"Increasing numbers of parents are expressing themselves in violent and abusive ways rather than sitting down with the headteacher and parents and working out what's the best solution."
The brawl comes after both the Conservatives and Labour have made General Election manifesto pledges to improve school discipline.
It also follows a decision by the English Schools Football Association not to invite England and Manchester United footballer Wayne Rooney to a prominent schools match because he was "not a good role model".
David Hart, the outgoing general secretary of the National Association of Head Teachers, endorsed the ESFA decision at the union's annual conference last weekend.