The closure will last for one week, according to the education minister.
More than 2 million pupils were already out of school due to the war which started in the northern region of Tigray last year, the government says.
As the fighting intensifies, government troops say they are taking towns from the Tigray rebels.
On Wednesday state forces announced they had recaptured the historic town of Lalibela, which contains churches that are Unesco world heritage sites.
In an interview with the BBC, an Ethiopian army commander said the country’s defence forces would not relent in their advances after recent gains.
The war has caused a humanitarian crisis with more than 300 schools that teach grade one to 12 destroyed as of October, according to a statement on the Ministry of Education’s Facebook account.
The government will work to restore the destroyed schools, the statement continued.
The war intensified after Tigray fighters said they were advancing towards the capital Addis Ababa in November.
They also launched an offensive to reach the Djibouti border in the east – which is crucial for getting supplies to landlocked Ethiopia.
This led to Prime Minister Abiy Ahmed saying he would join the war effort on the frontline, where he has since been pictured by state TV.