The Association of School and College Leaders (ASCL) have warned that proposed changes to give schools control over term times may turn into a "free for all".
The ASCL said schools currently follow the local authority calendar because it suits parents who have children in different schools.
The problem will come if no one is responsible for creating a coordinated calendar for an area and it turns into a free for all. Somebody needs to take the lead locally on deciding term dates and it makes sense for this to be the local authority, even if schools aren't required by law to follow it.
It would help for deregulation to be accompanied by guidance which reminds schools to take into account local circumstances and to consider the practical difficulties parents can face when schools within an area have varying term dates.
More top news
Even the help of rain delays could not save England's desperate attempt to push for a draw in Perth as the hosts claimed the series win.
Guillier conceded a "severe defeat" defeat to his supporters as the result came in.
The outage struck Hartfield-Jackson Atlanta International Airport at around 1pm local time, stopping all outgoing flights.