The country's vice president slammed health tourism just days after Buhari returned from a three-month medical break in the U.K.
Muhammadu Buhari had been in the U.K. on sick leave since May 7.
A lack of funding, cultural factors and traditions have been blamed for the estimated 10.5 million children not in school.
Buhari has been away for two months. Is his vice president, Yemi Osinbajo, preparing to succeed him?
Nigeria slipped into recession in 2016 after militants blew up oil facilities. But the government is trying to negotiate peace.
Ethnic tensions are boiling over in Nigeria. They did that before, and more than 1 million people died as a result.
Ethnic tensions have been on the rise after a northern Nigerian group called for the expulsion of Igbos, an ethnic group that made up the majority of the population of Biafra.
Eighteen charges of non-declaration of assets against Saraki, the head of Nigeria's senate, were dismissed after almost two years of legal wrangling.
Yemi Osinbajo called for an end to incitement after a call for ethnic cleansing that evoked the Biafran war, in which 1 million people were killed.
The West African country has been in recession since mid-2016.
Fifty years ago, Nigeria fought a brutal civil war based on ethnicity and secession. Those tensions continue to simmer.
A coalition of northern Nigerian groups called for the expulsion of Igbos, an ethnic group that largely supported the Biafran side in the 1960s civil war.
Muhammadu Buhari has been out of the country for almost three months in 2017 as Nigeria battles recession and insurgency.
Sixty people were killed during last year's protests to mark the anniversary of Biafran independence, according to the rights group.
Christian pastor Yemi Osinbajo is Nigeria's acting president while Muhammadu Buhari is on sick leave.
While a fragile truce is allowing Nigeria to step up oil output, a resolution of the crisis is unlikely without further concessions.
Muhammadu Buhari, 74, has rarely been seen in public since returning from seven weeks of sick leave in March.
After Nigeria's information minister sparked controversy with his comments on the dish, the vice president made clear who he thinks makes the best jollof rice.
Buhari has missed several cabinet meetings and is still recovering following a months-long absence in the U.K.
Buhari returned in March from a two-month medical absence in the U.K.
Nigeria has suffered from falling oil prices and a lack of foreign exchange.
The president said he would need to undergo "follow-ups" in the coming weeks.
Muhammadu Buhari, 74, left Nigeria on January 19 to undergo "routine check-ups" in the U.K.
Trade unions are angry about a 66 percent increase in fuel prices.
Much of Boko Haram's success has been down to the misappropriation of billions of dollars of Nigerian funds.
Power outages and long queues for fuel have been seen as militants sabotage oil pipelines.