“The Educational Role of School Principals in Improving the Quality and Productivity of Quality Management in Darussalam Private Middle Schools, Medan”. JUPE : Jurnal Pendidikan Mandala 8, no. 4 (December 2, 2023): 1235–1240. Accessed June 23, 2026. https://ejournal.mandalanursa.org/index.php/JUPE/article/view/6240.