for learning has existed since Classical antiquity. Formal schools have existed at least since ancient Greece (see Academy), ancient Rome (see Education in Ancient Rome) ancient India (see Gurukul), and ancient China (see History of education in China). The Byzantine Empire had an established schooling system beginning at the primary level. According to Traditions and Encounters, the founding of the primary education system began in 425 AD and "... military personnel usually had at least a primary education ...". The sometimes efficient and often large government of the Empire meant that educated citizens were a must. Although Byzantium lost much of the grandeur of Roman culture and extravagance in the process of surviving, the Empire emphasized efficiency in its war manuals. The Byzantine education system continued until the empire's collapse in 1453 AD. In Western Europe, a considerable number of cathedral schools were founded during the Early Middle Ages in order to teach future clergy and administrators, with the oldest still existing, and continuously operated, cathedral schools being The King's School, Canterbury (established 597 CE), King's School, Rochester (established 604 CE), St Peter's School, York (established 627 CE) and Thetford Grammar School (established 631 CE). Beginning in the 5th century CE, monastic schools were also established throughout Western Europe, teaching religious and secular subjects. In Europe, universities emerged during the 12th century; here, scholasticism was an important tool, and the academicians were called schoolmen. During the Middle Ages and much of the Early Modern period, the main purpose of schools (as opposed to universities) was to teach the Latin language. This led to the term grammar school, which in the United States informally refers to a primary school, but in the United Kingdom means a school that selects entrants based on ability or aptitude. The school curriculum has gradually broadened to include literacy in the vernacular language and technical, artistic, scientific, and practical subjects. Obligatory school attendance became common in parts of Europe during the 18th century. In Denmark-Norway, this was introduced as early as in 1739–1741, the primary end being to increase the literacy of the almue, i.e., the "regular people". Many of the earlier public schools in the United States and elsewhere were one-room schools where a single teacher taught seven grades of boys and girls in the same classroom. Beginning in the 1920s, one-room schools were consolidated into multiple classroom facilities with transportation increasingly provided by kid