The Hanoi middle and high school students, except those in sixth grade, were back after spending 10 months at home studying online.
For most, it was the first opportunity to meet friends and teachers since May last year, when the fourth Covid-19 wave hit.
Schools have in place safety measures like temperature checks at the gate and practiced actions to be taken in the event of infection.
All over the country, high school students returned to classes after Tet, while 57 out of 63 localities have also reopened middle schools.
In both Hanoi and Ho Chi Minh City, sixth graders and primary school and kindergarten students have yet to return to school.
They are expected to return next week in HCMC, on February 10 on the outskirts of Hanoi and February 21 in downtown districts.
Pham Quang Hung, head of the Ministry of Education and Training's international cooperation department, said reopening schools is inevitable since the vaccine rate is high now.
By mid-January two-thirds of countries in the Asia-Pacific had completely reopened schools, while the rest reopened partially, he said.
"Many countries encourage unvaccinated students to return to school. Japan and Singapore increased surveillance [of students] for symptoms, while Canada and the U.S. require Covid-19 testing results."
In Vietnam, most people aged 12 and above have received two shots of Covid vaccines.
The Ministry of Health is buying more doses to immunize children aged 5-12, and recommends that everyone should be vaccinated.