As we know from early historical accounts, and from the evidence of early woodcuts and engravings, Hogwarts students used to arrive at school in any manner that caught their fancy. Some rode broomsticks (a difficult feat when carrying trunks and pets); others commandeered enchanted carts and, later, carriages; some attempted to Apparate (often with disastrous effects, as the castle and grounds have always been protected with Anti-Apparition Charms); others rode a variety of magical creatures.
(Indeed, it is believed that the Thestrals currently living in the Forbidden Forest, and trained to pull the school carriages from Hogsmeade Station, are descendants of those ridden by students to school long ago.)
In spite of the accidents attendant on these various modes of magical transport, not to mention the annual Muggle sightings of vast numbers of airborne wizards travelling northwards, it remained the responsibility of parents to convey their children to school, right up until the imposition of the International Statute of Secrecy in 1692. At this point, it became a matter of urgency to find some more discreet method of transporting hundreds of wizarding children from all over Britain to their secret school in the Highlands of Scotland.