Schools in Cardiff will be among those across Wales that are ending the term after just three weeks on July 17.
Schools in the city were told on Friday night by the city council that the planned additional week of the summer term will not now take place in Wales' capital.
They are now having to redraw their plans to ensure they can get children back in just the three weeks between June 29 and the end of term.
Several other councils including Wrexham, Monmouthshire, Newport, Blaenau Gwent and Caerphilly are also telling schools not to open for the last week. On Anglesey schools won't even be going back on June 29 because of an outbreak of Covid-19 at the island's chicken processing plant.
However some councils will be asking schools, including those in Conwy, to operate for all four weeks of the planned shortened summer term.
It's understood that the Welsh Government was not able to reach an agreement with trade unions on the fourth week.
That has left the decision in the hands of councils, many of whom are not forcing the issue and are telling schools only to open for three weeks from June 29.
It means children will have very little time, perhaps just a few hours, in class before the end of the summer term.
On June 3, the minister for education Kirsty Williams had announced that schools in Wales would partially reopen for four weeks.
“Year groups will be split into cohorts with staggered starts and breaks. It is expected that this will mean, at most, a third of pupils present at any one time, though schools may need time to reach this level of operation," she said.
“There will be much smaller classes, providing secure dedicated time with teachers and classmates. This time will include online and personalised classroom experience, getting children and teachers ready for a similar experience in September.
“It is proposed that all schools will start the next phase on 29 June, with the summer term extended by a week, therefore the last day of term will be 24 July.”
Newport City Council has said opening a further week, until July 24, would be “unfair and potentially divisive”.
A spokesman for the council said: “Much work has been done with head teachers and governing bodies to put plans in place to meet the needs of the students, while ensuring the ongoing health and wellbeing of both students and staff.
“Local authorities are responsible for setting terms dates and we do not propose to ask teaching and other school staff to ‘volunteer’ during this week. Therefore Newport schools will close to pupils for the summer holidays on July 17.
“There is no contractual obligation on staff to work the extra week and this effectively puts the onus on head teachers and individual staff members which would, in our opinion, be unfair and potentially divisive at a time when schools face more than enough challenges.
“There is no guarantee that all schools will be in a position to adequately staff provision in the fourth week on a voluntary basis.
"Clarity is required for schools, parents and young people in order to approach the next weeks with confidence and for parents to have the opportunity to make alternative childcare arrangements as required in the fourth week. This is not something that can be left to the last minute.”
In Caerphilly, meanwhile, the decision has been taken as part of a “consistent approach”.
“The original proposal was for pupils to return for a period of four weeks, however, after extended discussions we have concluded that our schools will now open for three weeks and close for the summer holidays on July 17,” said council leader Philippa Marsden.
“We are taking a consistent approach across Gwent and I very much welcome this opportunity for pupils to check in and catch up before the summer break. Our priority is to safeguard the health and wellbeing of pupils and staff, as well as ensuring learning can resume as quickly and safely as possible.”
Blaenau Gwent has said that it has made its decision in order to “provides certainty” to staff and parents.
Councillor Joanne Collins, executive member for education at Blaenau Gwent Council, said: “We’re working closely with all our schools in order to welcome back groups of learners for ‘check in, catch up’ sessions, in order to help prepare them for September.
"The main focus of the sessions will be the well-being of our children and young people and for teachers to assess where pupils are with remote learning.
"The Council has today made a decision that the current school term in Blaenau Gwent will formally end on Friday, July 17 as originally planned.
"This decision is an approach that is being reflected across the Gwent region, and indeed across Wales, and we believe provides certainty to school leaders, teaching staff and parents so that they are able to effectively plan ahead.”
Some councils have maintained that they will be open until the original date issued by the Welsh Government of July 24, although not all have issued updates in recent days so their stance could be subject to change.
