studied after studying the post-16 education level. The Programme for International Student Assessment coordinated by the OECD currently ranks the overall knowledge and skills of Spanish 15-year-olds as significantly below the OECD average of 493 in reading literacy, mathematics, and science. Health The health care system of Spain (Spanish National Health System) is considered one of the best in the world, in 7th position in the ranking elaborated by the World Health Organization. The health care is public, universal and free for any legal citizen of Spain. The total health spending is 9.4% of the GDP, slightly above the average of 9.3% of the OECD. Religion Roman Catholicism, which has a long history in Spain, remains the dominant religion. Although it no longer has official status by law, in all public schools in Spain students have to choose either a religion or ethics class. Catholicism is the religion most commonly taught, although the teaching of Islam, Judaism, and evangelical Christianity is also recognised in law. According to a 2020 study by the Spanish Centre for Sociological Research, about 61% of Spaniards self-identify as Catholics, 3% other faiths, and about 35% identify with no religion. Most Spaniards do not participate regularly in religious services. A 2019 study shows that of the Spaniards who identify themselves as religious, 62% hardly ever or never go to church, 16% go to church some times a year, 7% some time per month and 13% every Sunday or multiple times per week. Recent polls and surveys suggest that around 30% of the Spanish population is irreligious. The Spanish constitution enshrines secularism in governance, as well as freedom of religion or belief for all, saying that no religion should have a "state character," while allowing for the state to "cooperate" with religious groups. There have been four Spanish Popes. Damasus I, Calixtus III, Alexander VI and Benedict XIII. Spanish mysticism provided an important intellectual resource against Protestantism with Carmelites like Teresa of Ávila, a reformist nun and John of the Cross, a priest, taking the lead in their reform movement. Later, they became Doctors of the Church. The Society of Jesus was co-founded by Ignatius of Loyola, whose Spiritual Exercises and movement led to the establishment of hundreds of colleges and universities in the world, including 28 in the United States alone. The Society's co-founder, Francis Xavier, was a missionary who reached India and later Japan. In