Norway was among the first countries in Europe to open up nursery schools on April 20, followed by schools for the youngest pupils, between ages six and 10, the following week.
The reopening of the schools, which closed on March 12, was originally met with concern among parents.
A Facebook group called "My child should not be a guinea pig for COVID-19" gained almost 30,000 members.
"We have so far not seen that opening nurseries and schools have had a negative effect on the infection situation," Frode Forland, a senior official from the Norwegian Institute of Public Health, told a daily press briefing.
"If the opening would have had a negative effect we would have begun to see that in an increased number of infections," Forland added.
The same seemed to be true for hair saloons, physiotherapists, as well as some other healthcare-related professions which have been allowed to operate since April 27, according to Forland.
Forland however stressed that it might be a little too early to gauge whether the opening would lead to an increase in hospitalisations.
The rest of the country's primary schools, high schools and colleges are due to reopen later in the week.
The children who have returned to classrooms and nurseries have done so under strict new health guidelines.
Children must be kept in small groups that do not physically interact with each other, physical distancing measures have been introduced and hygiene is stressed.
As of Monday Norway had confirmed 8,106 cases of the novel coronavirus, and 224 people have died in the country of 5.4 million people.