How is social stratification achieved through caste system?

In a Caste System, status is determined by birth and is lifelong. Someone who is born into a low-status group will always have low status, no matter how much that person may accomplish in life. In sociological terms, a caste system is built on ascribed status. Achieved status cannot change an individual's place in this system. Societies with this form of stratification try to make certain that the boundaries between castes remain firm. They practice endogamy, marriage within their own group, and prohibit intermarriage. Elaborate rules about ritual pollution--touching an inferior caste contaminates the superior caste--keep contact between castes to a minimum.