Most children have been learning at home since schools closed before Christmas.
Wales’ youngest pupils are returning to the classroom in the first step towards reopening schools.
Most children have been learning from home since December after a sharp rise in Covid cases.
Children aged three to seven are starting a phased return to face-to-face teaching, along with some students on practical college courses.
Education Minister Kirsty Williams said on Sunday she hoped more pupils would return if cases continued falling.
The Covid case rate in Wales is currently 83 per 100,000 people – the lowest of the UK nations – and Wales’ R number is between 0.7 and 0.9, Public Health Wales estimates.
A decision on the return of other primary school children and older pupils is due to be made on 15 March.
Lisa Freeman’s four-year-old son Ethan was returning to his reception class at Ysgol Hamadryad in Cardiff on Monday.
She said he was “very nervous” and he did not really talk about going back to school, so they had “broached the subject slowly”.
“He’s struggled with the online lessons,” Ms Freeman said.
“I think, as a four-year-old, being sat behind a computer screen has been very difficult for him. He just didn’t engage as much as we would have like him to.”
Ms Freeman said she was concerned there would be further school closures as it had “very much affected him”.
“Hopefully this is the last time – I think it would be really harmful to pull him out of school again,” she said.
“He hasn’t left my side since the beginning of December really. I think it’s quite frightening, we try to keep the news off as much as possible [around him].
“Just to be around his peers I think is huge for his age group.”
Victoria Rosser, from Cwmbran, whose five-year-old son will return on Thursday, said she was not sure if it was the right time for children to return.
“I’m a little anxious as I’m a shielding parent who hasn’t received the second vaccine, however, I feel more confident than I did in September,” she said.
Ms Rosser, a former teacher, said her son was excited but also “a little nervous” to return to school.
“Even though he’s in Year 1, he’s only spent just over half a year in school,” she said.
“Children of similar age, who haven’t had the opportunity to learn at home, could have had changes made to their neuro pathways forever.
“So even though I’m scared to send my son back to school, I will, because we are yet to learn the damage it has done to them.”
The Welsh Government said under the current circumstances punitive measures, including fines, would not be appropriate.
It said some authorities might deem it necessary to pursue “a small number of cases relating to persistent absence” which were unrelated to the pandemic and where there were concerns about the welfare of the child.
Teaching staff will now be tested twice weekly for Covid, and £5m will be spent on face coverings and other equipment.
Ty Golding – head teacher at Ysgol y Ddraig in Llantwit Major and Holton Primary School in Barry, Vale of Glamorgan – said his staff were “excited” at returning to school and “addressing those wellbeing and learning needs”.
But he acknowledged some parents and staff still needed reassuring.
“The biggest challenge for us – which hopefully will be incident-free and quiet and all about settling back in – is winning hearts and minds in the community with parents and staff, making sure everyone feels safe and secure,” he told BBC Radio Wales..
Asked whether he felt teachers and school staff should be prioritised for a Covid-19 vaccine, Mr Golding said he did, adding it was important they felt “a sense of prioritisation”.
Ministers said children aged three to seven had been prioritised to return to school first, due to evidence showing Covid spread less quickly among the youngest children, who can also be more difficult to teach remotely.
The Welsh Government had said it expected to see pupils returning from Monday but it would be “done in a phased and progressive way”.
Primary schools in some parts of north Wales have said they would not have children back until later in the week, after concerns over higher case rates.
Wrexham, Anglesey, Denbighshire, Gwynedd and Flintshire are delaying the immediate return of younger pupils – with pupils back in class by Friday.
Ceredigion, the county in Wales with the lowest case rate, is also operating a phased return where children will attend for one day in the first week with a full return expected from 3 March.
Ms Williams said the next Welsh Government review would look at whether older exam year pupils could return, alongside the remaining primary school year groups. That includes Years 11 and 13, and college students.
Ms Williams said: “Our priority will be to use whatever headroom we have to maximise face-to-face learning for Years 11 and 13, and many head teachers that we’re consulting with would like some flexibility to get some Year 10 and Year 12 students in as well.
“But we might have to do that on a routine basis, allowing us to cut the number of children in the class down, helping to keep those schools as Covid-secure as possible.”
Ms Williams also said some university students were due to return to campus this week for practical assessments.
She said the Welsh Government was working with universities “to bring back students when it’s safe and appropriate to do”.
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