The study explored how mathematics learning loss took place among Turkish middle school students during the COVID-19 school closures through mathematics teachers’ self-reported practices, challenges, and efforts while they were trying to support their students’ learning. Interviews with 19 public and 9 private middle school mathematics teachers indicated that there were certain differences in teachers’ practices and revealed the existing inequalities among the schools, classrooms, and students. Students’ lack of participation, teachers’ limited use of methods to teach mathematics, the socio-economic status of families and their lack of collaboration with teachers were among the reasons for mathematics learning loss.