A move to allow schools to set their own term times will make life harder for families with children of different ages, a survey of parents suggests.
Three-quarters of parents say that government plans to give all state schools the freedom to decide on terms and holidays will make it tougher for those who have children at more than one school to arrange childcare and family activities.
Under the proposals, contained in a new Deregulation Bill, from September 2015 local councils will no longer be able to tell their schools when terms should start and end.
The change paves the way for individual schools to introduce longer terms and cut school holidays.
But the new survey, conducted by parenting website Netmums and the 4Children charity, suggests worries among parents that schools will organise their holidays differently.
More than three-quarters of those questioned (77.1%), said they were concerned that a major change to holiday dates could mean schools organising terms differently, which would make it harder for parents with children at more than one school.
The poll also found that parents were split on whether school holidays should be changed.
Around one in seven (13.7%) wanted a shorter summer break and a longer Christmas holiday, three per cent said the Easter holiday should be longer, around a third (33.8%) wanted the weeks off split more evenly throughout the year, a similar proportion (38.2%) said there should be no changes and just over one in 10 (11.3%) said children should get fewer weeks off in general.
Currently, state school pupils usually get two weeks off at Christmas and Easter as well as six weeks in the summer, and three week-long half-term breaks. School days usually run from 9am or earlier to 3pm, or 3.30pm. Academies and free schools have already been given the authority to change their term dates.
Ministers have argued that schools are best placed to decide on their holidays and the system should be changed.
Some parents suggested that local schools will need to communicate with each other to co-ordinate holidays.
Sarah Ockwell-Smith, mother of four and parenting author, said: "It is already difficult for parents to work and entertain their children during the holidays but with the changes to school holidays coming into place, it will prove impossible. Schools need to communicate with one another and ensure they take the views of parents on board too."
Netmums editor-in-chief Cathy Ranson said: "While there may be a genuine need to look at spreading holidays more evenly throughout the year, holiday dates must be strictly co-ordinated so parents can plan childcare.
"It is already tough for parents to find employers with the willingness and flexibility to let them arrange adequate summer care at an affordable price, so spreading the number of weeks when kids could be off over summer will only drive more mums out of work."
The poll also asked parents about government plans to clamp down on term-time holidays.
At the moment, headteachers can grant up to 10 school days leave a year for family holidays in special circumstances, but from next month this will be changed to remove the reference to holidays and the 10 -day threshold, and to say that school leaders cannot grant any absence during term times unless there are exceptional circumstances.
The survey found that 43.9% of parents say this will have some impact as they occasionally take their child out of school in term-time, while a further 4.9% said it will have a huge impact.
More than a third (38.1%) of those who took their child out of school during term time had done so for a cheaper family holiday, while 40% said it was for a special occasion, such as a wedding or funeral.
The survey, conducted through the Netmums website, questioned 1,190 parents in July.
A Department for Education spokesperson said: "It is fantastic to see in this survey that more than 60% of parents want schools to use their new freedoms to change term dates.
"Headteachers know their pupils and parents best and we trust them to respond to parents' views."