hóng is archaic. It named the village or county academies of antiquity (Han through Tang), where boys learned the Classics. Surviving compounds:
黉学 (the academy / its students),
黉门 (the academy gate — by metonym, the school itself),
黉舍 (school buildings). In modern Chinese the standard words are
学校 or
书院 (for academy);
黉 is used only in deliberately classical or literary register, often for poetic effect or in restoring period flavour.