One of them is the French school system – the idea is that the French school system teaches the same cultural values and history to all children, regardless of whether their parents are immigrants or if their family has been living in France for generations and generations. Another institution traditionally important to the assimilationist model is obligatory military service. Until 2002, all French men were required to serve in the army for a period of time, the idea being that service in the military is conducive to feelings of national identity and pride, and thus helps assimilate the young men required to serve into French society and culture. Under the administration of French President Jacques Chirac military service in France was made voluntary (legislation was set in place in 1996 to professionalize the French army, and in 2002, conscription was halted indefinitely). The current French president, Emmanuel Macron, has said that he is in favor of re-establishing a period of obligatory military service. There is also the French Foreign Legion which allows foreign nationals to serve in the French army and ultimately gain French citizenship for doing so.
Another important piece of the French assimilationist model is the concept of laïcité (secularism). Laïcité can perhaps be described as the French version of the idea of separation of church and state. France is traditionally an overwhelmingly Catholic country and, according to notes from my French foreign and European policy class, during the days of the French monarchy, the Catholic church was generally best friends with the various French kings.