What is the four main schools in Shiites?

Answer 1

each religion possesses a certain number of primary principles, which form its essential basis and other principles of secondary importance. when the followers of a religion differ as to the nature of the primary principles and their secondary aspects but preserve a common basis, the result is called division within that religion. such divisions exist in all traditions and religions, and more particularly in the four revealed religions of Judaism, Christianity , Zoroastrianism and Islam.

Shiism did not undergo any divisions during the imamate of the first three Imams: Ali , HAsan and Husayn. but after the martyrdom of Husayn, the majority of shiites accepted the Imamate of Ali ibn Husayn Al- Sajjad , while a minority known as Kaysaniyyah believed that the third son of Ali, Muhammad ibn Al-Hanafiyyah was the fourth Imam as well as the promised Mahdi and that he had gone into occultation in the Rawdah mountain and one day would be reappear. after the death of the Imam Sajjad , the majority of shiites accepted as Imam his son, Muhammad Al-Baqir while a Minority followed Zayd Al-Shahid, another son of Imam Sajjad and became known as Zadyis. following Imam Muhammad Al-Baqir , the shiites accepted his son JAfar Al-SAdiq as Imam and after the death of Imam Jafar, The majority followed his son Imam Musa al-Kazim as the seventh Imam. however , one group followed the older son of the sixth Imam, Ismail, who had died while his father was still alive and when this latter group separated from majority of Shiites , it became known as Ismailis. others accepted as Islam either Abdullah al-Aftah or Muhammad, both sons of the sixth Imam. finally another party stopped with the six imam himself and considered him as last imam. in the same way, after the martyrdom of Imam Musa al-Kazim, the majority followed this son, Ali al-Rida, as the eighth imam . however , some stopped with the seventh imam and became known as WAqifiyyah. from the eighth imam to twelfth the majority of the shiites believed to be the promised Mahdi,no division of any importance took place within shiism.