The Educational Role of School Principals in Improving the Quality and Productivity of Quality Management in Darussalam Private Middle Schools, Medan. Jurnal, Pendidikan [Internet]. 2023 Dec. 2 [cited 2026 Jun. 23];8(4):1235-40. Available from: https://ejournal.mandalanursa.org/index.php/JUPE/article/view/6240