Basirat Olamide Ajayi, a math teacher in Lagos, Nigeria’s biggest city, has come up with a way to help students prepare for crucial exams amid Covid-19, reports AP. She began offering free mathematics classes online via Twitter, WhatsApp and Instagram. And now, after almost six months, more than 1,800 students at various levels are taking her classes — across Nigeria and even internationally.

Students watch her short math videos — no more than 5 minutes long — and respond to her questions. She will send them homework, and occasional assignments. And she grades them.

“Sometimes, I stay awake till 2 a.m. going through their assignments!” she said.