I don't think that there is a specific quota for Muslims and Christians at Nation level examinations. Though in some states there are some reservations for them. Like: In Tamil Nadu: As Christians are there in good numbers. They count as a vote bank to the parties. In Andhra Pradesh: The population of Muslims are high in Andhra Pradesh. In Kerala: Muslims as well as Christians are in good numbers here. They have allotted a reservation to them in the name of minorities(as the parties try to show). But a thirst for votes is a matter for their reservation in these states as they together make a good % of vote banks in these states.