Wales is following a phased approached to returning to face-to-face learning, unlike in England where pupils will all go back on March 8.
The Welsh Government's Education Minister Kirsty Williams said it was her preference to see a complete return after the holidays, which end on April 12.
Three-to-seven-year-olds across most of Wales are going back to their desks over the next few days.
However, in the Wrexham County Borough, which includes Chirk and the Ceiriog Valley, the return has been delayed until at lease Friday because of the high rate of positive cases in parts of the borough.
Recently those figures have been falling.
Other primary pupils, and years 11 and 13, are due to return in Wales on March 15 if Covid case rates continue to fall.
Ms Williams told a press conference that pupils in years 11 and 13, and those in further education settings, will be tested twice a week, alongside education staff.
Plaid Cymru has this week called for the vaccination of all staff working in schools.
Parent across Powys were told that outdoor learning would be a larger part of the younger childrens' return to school.
Councillor Phil Davies said: "As learners return after the half term holidays, parents and carers are being asked to dress their children in warm clothes that are suitable for outdoor learning and so that schools can maintain ventilation for the safety of learners and staff.
“The safety of our learners and school staff is our main priority. We have been working with our school leaders and helping them prepare for the return of learners to school and early year settings.
“As schools prepare for the phased return of learners, it is crucial that all families play their part by following the guidance here in Wales and do not mix outside of school to prevent the spread of Covid-19."