More than half of Scots schools have reported at least on coronavirus case among pupils in the first two weeks of term.
New figures from a freedom of information request by the PA news agency submitted to Public Health Scotland (PHS) show that 1,455 schools in Scotland recorded a positive case between August 16 and August 27, the first two weeks of term - 58.7% of all schools.
According to Scottish Government figures released in December, there are 2,476 schools registered in the country.
While it is not clear how many of the cases in schools were contracted there as opposed to the community, First Minister Nicola Sturgeon has repeatedly said the return of schools in Scotland contributed to the spike in Covid-19 cases seen in recent weeks, which she said this week has shown signs of dissipating.
Meanwhile, PHS data also shows nearly 15% of cases during the same time period could be linked to an educational setting, a nursery, school, college or university, although higher education had not yet returned for the new term during the time the data covers.
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A total of 8,113 positive cases during the first two weeks of the school term reported having been in an educational setting in the seven days before they developed symptoms, 14.2% of the cases reported during that time.
Larry Flanagan, the general secretary of the EIS teaching union, said: "Since pupils and staff returned to schools last month, we have seen a substantial increase in Covid infection rates across the country.
"There have been significant outbreaks linked to schools, with Covid-related absence rates amongst pupils and teachers at record high levels.
"This highlights the continuing need for appropriate safety mitigations in our schools to reduce the infection risk, and also confirms the importance of continuing the vaccination programme including the planned roll-out of the availability of vaccines for 12 to 15-year-olds."
Despite the new figures, Tory education spokesman Oliver Mundell said it was important that schools remain open, but that measures are put in place to limit the spread.
"An increase in cases was expected when schools returned. But the SNP-Green Government need to ensure that they are striking a balance of mitigating the risk of case numbers against causing further disruption to education.
"The World Health Organisation and the children's commissioner are clear that for young people's mental health and wellbeing, and for some their safety, the number one priority must be to keep schools open.
"The SNP-Green Government need to guarantee that every robust measure is in place to keep our schools as safe as possible from being a place where the virus is transmitted.
"That will ensure that in-person learning can continue and pupils will hopefully return to a normal learning experience as quickly as possible."
Both the Scottish Greens and Lib Dems said the decision to offer vaccines to young people aged between 12 and 15, announced by First Minister Nicola Sturgeon earlier this week, would be vital to keeping youngsters safe.
"There is a real risk of disruption to pupils' education if these outbreaks are not swiftly crushed," said Lib Dem education spokesman Willie Rennie,
"That's why it will be so important to encourage young people to come forward and get their vaccines."
Green education spokesman Ross Greer said: "The decision to offer Covid-19 vaccinations to most secondary school pupils will certainly help reduce this disruption, if its rollout is swift.
"However, the Government really needs to get to grips with the slow progress on improving ventilation in schools, a matter I've repeatedly raised with the First Minister.
"We must do everything we can to make our schools safe for both pupils and staff."
A Scottish Government spokeswoman said: "We continue to closely monitor the impact of Covid-19 cases in schools.
"In light of the latest data and evidence, we have decided to extend the period for safety mitigations in schools to remain in place until at least the October holidays.
"We have also strengthened guidance for staff and pupils identified as being low-risk contacts of positive cases.
"They are now being asked to take a Lateral Flow Device (LFD) test before coming back to school. This is in addition to current advice for staff and secondary pupils to take an LFD test twice a week and to record all results.
"The current rate of Covid-19 related absences among pupils is around 4%. It remains the case that the vast majority of Covid-19 absences - about 69% - are pupils who are isolating, with around 28% being due to Covid-related sickness."