Sistema educativo de México

Article 3 of the 1917 Constitution sets out the guiding principles of education in Mexico: it must be compulsory, secular (laica), and free of charge in public schools. ‘Secular’ means public education is kept independent of any religious doctrine, a principle rooted in Benito Juárez’s Reform era.

Don’t confuse this with the question about which school levels are compulsory — here the exam wants the three defining characteristics of education.