MANDERA, Kenya — In a small classroom at Mandera Academy, a private school, posters with numbers, the Swahili and English alphabets, and geometric shapes hung on the walls as dozens of students crammed together on small wooden desks.

Bilan Abdi, 9, stood up and spoke about her teacher, Violet Muranga, who was shot dead last year as she was dragged out of a bus with other victims while traveling to visit her family.

“We learned a lot from her,” Bilan said softly. “Songs like ‘Twinkle, Twinkle, Little Star.’ ”

Kenya has suffered mightily at the hands of the Shabab, a Somali Islamist extremist group whose deadly attacks have left a painful void in this region’s schools.

Many of the 28 people killed on the bus, including Ms. Muranga, were teachers in the area heading home for Christmas break. Their deaths came around the same time as an attack at a mine in this northern corner of the country, where dozens of workers were separated by religion, forced to lie face down and shot dead.