NELLIE PEYTON and KIM HARRISBERG IN rural Sierra Leone, teenagers tuned into solar-powered radios for their lessons, while Kenyan students texted a code to receive free learning guides on their phones. As COVID-19 shut Africa's schools, governments and charities rushed to make learning accessible to millions of pupils without internet or even electricity, sparking innovations that could keep children learning long after the pandemic has passed. "The situation... pushed all the governments and education ministries to think in a different way," said Elena Locatelli, an advisor on education in emergencies at the U.N. children's agency UNICEF. In a matter of…