It’s the first time they’ve been back since mid-December, when the country declared a second wave of new infections.
The academic calendar has been staggered after schools were closed for more than six months last year due to the pandemic.
University students are also resuming face-to-face learning on Monday. They have been at home for nearly a year due to a strike by lecturers.
Lawmakers had earlier asked the federal government to postpone the planned reopening of schools by three months because of the rising number of coronavirus cases.
The country has recorded more than 10 000 new infections in the last seven days.
A total of 110 387 cases have so far been confirmed, with 1435 deaths.
Across Africa, cases are continuing to rise, particularly in South Africa, Zimbabwe, Sudan and the Democratic Republic of Congo.
--BBC--