I don't think procuring food for the students at Hogwarts is a plot hole. As TenthJustice mentions, food can't be summoned from thin air. It can be moved to location to location, if the summoner knows the origin of the food, in other words where the food is to begin with.
In Deathly Hallows, Dolores Umbridge mocks Mary Cattermole (a Muggleborn) because Mary's father was a Greengrocer (sp?), i.e. a grocer. That Umbridge knows what a grocer is suggests the wizarding world probably has the equivalent. As well, the population of witches and wizards is much, much lower than that of the general British public -- not as much food would be necessary for Hogwarts, although it's certainly clear in the books that they eat well and in large quantities!
Food could be summoned.
Food could be purchased, say weekly, and brought to Hogwarts either by the supplier or perhaps Hagrid or Mr. Filch (there would have to be a non-magical means of transport for Filch to do it).
The Hogwarts Express, I believe, according to J.K. Rowling, is reserved for transporting the students between Hogwarts and London and being utilized for the rare special occasion/trip (Pottermore? Interview? I remember her saying something about the Hogwarts Express and a Celestina Warbeck concert. I will look for the source!). It does not make daily trips to Hogwarts; it's a specialized train reserved for infrequent use.