Original sentence: In the late 20th century, "community kolels" were introduced.They are an Orthodox outreach tool, aimed to decrease assimilation and propagate Orthodox Judaism among the wider Jewish population
Edited sentence: Beginning in the last third of the 20th century, the kolel concept expanded with the introduction of community kolels.Community kolels are a kiruv (Jewish outreach) tool which aims to increase Jewish knowledge and identity as a hedge against assimilation.Community kolels are typically composed of a minyan of students who engage in advanced Torah study with their own rabbis and shiurim for part of the day, and then conduct one-on-one learning sessions, free classes, and holiday activities for the Jewish community at large during the other part of the day