Is it permissible to establish a private Islamic school in France that adheres to the French curriculum and adds Islamic and linguistic subjects, with the aim of teaching Islam and avoiding mixing, and would assisting those in charge of it be considered incitement to migrate to and remain in infidel lands?

If it is established that the goal of the school is to teach Islam and avoid forbidden mixing, then assisting in its establishment is desirable or obligatory. Describing this assistance as incitement to migrate to lands of disbelief is far from fair, for migration existed before the school, and the school is not a cause for migration. Migration to lands of disbelief and staying there with the intention of spreading the Islamic call and safeguarding Muslims from deviance is considered a righteous act.