Analisis peran dan efektivitas Organisasi Siswa Intra Sekolah (OSIS) SMAN 21 Jakarta dalam mengembangkan status Rintisan Sekolah Bertaraf Intemasional (RSBI) SMAN 21 Jakarta = Analysis of the role and effectiveness of Intra-School Student Organizations (OSIS) of 21 State Senior High School (SMAN 21) Jakarta in developing SMAN 21 Jakarta's Intemational Standard School Pilot (RSBI) status