Sect is fine. It is not derogatory. Also branch or movement can be used. The first centuries of Islam gave rise to three major sects: Sunnis, Shi'as and Kharijites. Kharijites were initially divided into five major branches: Sufris, Azariqa, Najdat, Adjarites and Ibadis. Among these numerous branches, only Hanafi, Maliki, Shafi'i, Hanbali, Imamiyyah-Ja'fari-Usuli, Niza