If school was out for summer in Westeros, it might just be out for years and years. This is part of the fantastic "Setting" of Westeros: the seasons last for years – though for how many years is anybody's guess, as that constantly changes. When the book begins, the current summer has already lasted nine years (2 Bran 1.1). In fact, the maesters at the Great Citadel are responsible for keeping track of when summer is ending, though they're about as accurate as most weathermen. And there's even a legend that one of these summers will be an endless one (26 Eddard 5.4), with no homework and lots of surfing.
But summer and winter also happen to be symbols in this book. We can tell by how often these seasons get connected to one of our favorite themes, "Coming of Age". For instance, Bran is called "a sweet summer child," indicating that he's lived a relatively pain-free and fear-free life (until, of course, the accident) (25 Bran 4.16). Jon Snow is also something of a summer child, since he has lived most of his life in this summer (53 Jon 7.58). The older members of the Night's Watch mention that the new recruits still "smell of summer"; that is, they are untested and weak, not used to the sorts of dangers of the north and of winter (see 20 Jon 3, 42 Jon 5, and 49 Jon 6).
Eddard connects childhood to summer as well: "Summer will end soon enough, and childhood as well" (7 Catelyn 2.104). Now wait a minute. Remember the Stark motto? "Winter is Coming." If summer is childhood, then what is Winter? Adulthood? Yeah: making compromises, facing (and possibly being beaten by) monsters, having to deal with the Lannisters, the list goes on (and includes, of course, death). So we guess they're lucky that it's been such a long summer.