Nearly 17,500 children were tested for coronavirus across Scotland over the past week - but only 49 were positive, Nicola Sturgeon has said.
Demand for testing has increased "significantly" since pupils returned to schools earlier this month
But the first minister said the 49 children aged between two and 17 who tested positive last week was only two more than the previous week.
This was despite a 300% increase in the number of children who were tested.
Ms Sturgeon said this underlined that parents and teachers should not be "unduly concerned" about the return to school.
The total number of people who have tested positive for coronavirus in Scotland has now passed 20,000, with a further 68 positive results over the past 24 hours.
A huge rise in demand for coronavirus tests has seen some people in Scotland told they must travel hundreds of miles - including to England and Northern Ireland - to attend a testing centre.
Ms Sturgeon said the number of children and young people being brought forward for tests had "increased significantly" in the two weeks since schools reopened.
"Last week alone, just short of 17,500 young people between two and 17 were tested," she said.
"That is a very significant number, but the key point I want to make from that is that of those, only 49 tested positive. That is a positivity rate of 0.3%."
Image copyright Getty ImagesThe first minister said she could "well understand why many parents and teachers have a concern about the return to school".
But she said the figures revealed "the bigger picture", adding: "Despite an increase of more than 300% in testing of young people from one week to the next, the number of positive cases recorded increased by just two.
"That is encouraging, and I hope it's reassuring to parents and teachers across the country. I hope it will encourage people to absolutely continue to be vigilant, but not to be unduly concerned about young people in schools."
Ms Sturgeon urged parents to "remember the symptoms that trigger the need for a test", saying that a runny nose alone should not lead people to get tested.
School closure
There have been concerns about clusters of the virus linked to schools, such as Kingspark School in Dundee which has had to be closed.
A total of 34 cases have now been linked to the school, including 21 staff and three pupils, but Ms Sturgeon said there was "no evidence of wider community transmission" of the virus.
The Scottish government has changed its guidance to recommend that pupils in secondary schools wear face coverings in corridors and communal areas from Monday of next week.
However ministers believe the spread of the virus is a bigger issue outside of schools, with the police to be given new powers from Friday to break up house parties.
Ms Sturgeon said "these kind of gatherings pose a significant transmission risk".