Two weeks after the reopening of schools, some pupils are showing signs of mild trauma from the lockdown.
Otago Primary Principals' Association president Shelley Wilde said it might be another four to six weeks before more moderate signs of trauma appeared among children.
She said the vast majority of children were pleased and happy to be back at school, and had responded well to the new "safe normal" hygiene and physical-distancing practices.
However, some pupils were anxious about things such as making sure their hands were clean all the time, and some were taking advantage of the Chatbus (a counselling service for children) who might not have before.
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"Some of that might be related to relationship difficulties that occurred during lockdown," she said.
"It's not obvious. I think it's still too early to tell. At the moment, they're happy to be back together and realise they love school.
"But I think we'll be looking more in the next four to six weeks, to see if there is any more medium-term trauma."
Similar behaviour was being seen among teenagers, Secondary Principals' Association president Linda Miller said.
"The majority of students have come back into school and are catching up, but certainly we're seeing increased numbers of students accessing counselling and things like that.
"So for some students, it's been a pretty rugged time in lockdown.
"There's certainly higher rates of anxiety, which manifests in all sorts of ways.
"It may be panic attacks or anxiety about being in close proximity with other people."
Adding to that stress were concerns about getting behind with NCEA studies.
"Some students have managed to keep up really well. Other students have had to take responsibility for younger siblings during the lockdown, and have simply not been able to keep up with their schoolwork.
"So there's a huge variation in terms of where kids are at and what we're dealing with, from both an academic perspective as well as a pastoral perspective."
Ms Miller said pastoral staff were working hard on supporting those pupils and she was confident they would get back on track academically.
Mrs Wilde said most primary schools were not comparing children's academic learning with where it was pre-lockdown.
"The big focus has been on going slowly but surely — making sure that parents, teachers and children all feel comfortable with the new safe normal.
"The children have been doing a lot of creative ... unpacking of what the last few weeks have been about, and not really delving too deep just yet."
She said not all children engaged in distance learning during lockdown, but many did.
"Those that did, have come back ready to keep on firing. They've realised that they can do a lot at home.
"They do appreciate that they need a teacher to take them further and delve deeper, but I think they've also become a lot more cognitive in self-directed learning — more independent."
Southern District Health Board mental health, addictions and intellectual disability medical director Dr Evan Mason said the mental health impacts of Covid-19 and the lockdown would be felt for years.
"We clearly saw that in Canterbury in the period after the earthquakes, that particularly young people were affected for years afterwards."
That could mean higher rates of anxiety and depression, and a focus on enhancing primary frontline services for people to access, he said.
The Government has already funded a range of initiatives, from apps to resources for talking about the virus with children.