A San Francisco school vice principal is donating one of her kidneys to a former student, who was diagnosed with end-stage renal disease last fall at the age of 19. 

Christine Buell, a 45-year-old vice principal at the Sacred Heart Cathedral Preparatory School and a mother of two young girls, is donating the organ to a former student, Kelvin Sanders, the Washington Post reports.

Buell reportedly heard about Sanders’ situation eight months ago while browsing her Facebook feed.

As a teacher for more than 20 years, she is Facebook friends with a lot of her former students — some 500 to 600 of them.

And after several months of testing, Sanders turned out to be a good match as an organ donor for Sanders, who graduated in 2013.