Congo restarted the academic year Tuesday in Ituri, the Ebola epicenter, even after the teachers' union urged a delay and some government-run schools saw sparse attendance.
2,950 people have died among 6,100 confirmed cases since mid-May, and parents in Bunia said they were keeping children home because they saw too few added prevention measures.
UNICEF said it is helping schools limit transmission with thermometers, sanitizer and hand-washing stations, but many campuses still lack clean water and remote areas face delivery delays.
Children 4 and under have a 60% case-fatality rate, underscoring the risk as the Bundibugyo-virus outbreak spreads across more than 60 health zones without an approved vaccine or treatment.
The outbreak is already the fastest in Ebola history, and WHO says it is on track to surpass West Africa's 2014-2016 regional epidemic as strikes, conflict and attacks on health workers hamper the response.