The 36-year-old actress will lead the cast including Greg Austin, Fady Elsayed, Sophie Hopkins, and Vivian Oparah, who all will play the students, reported Variety.
Kelly will play a teacher at Coal Hill School, an institution that has been part of the "Doctor Who" universe since its inception in 1963.
"We searched far and wide for this amazing cast, fantastic actors, who understand what we're aiming for with this show.
And how lucky we are to get Katherine Kelly! She's been stunning in Happy Valley, The Night Manager, and Mr Selfridge, just wait until you see her here," show creator Patrick Ness said.