It is probably significant that the boys at Mr. Deasy's school play "Hockey," rather than the Irish game of hurling. The two sports are similar, but hockey is English. Its place in the curriculum marks one more way in which the school is inculcating Unionist values.
Although its origins are ancient, field hockey assumed its modern form in the 19th century in English public schools. The more rugged and dangerous sport of hurling has been a part of Irish life for thousands of years, sharing many features (field, goals, number of players, some terminology) with Gaelic football. The Gaelic Athletic Association sought to revive it as part of the broader Celtic Revival, and its efforts proved hugely successful over the course of the 20th century.
Nationalist political implications aside, hockey will do just as well as hurling, slightly later in the chapter, for conveying Joyce's view that field sports are "mimic warfare" preparing boys for battle.