I think they should make you read King Lear when you're expecting your first child. Screw the high school classroom -- who has kids then? (Well, lots of people do, but that's another matter entirely.)
But seriously, the relevance of King Lear's themes is a function of the reader's age. Maybe a 16-year-old kid doesn't care if Lear was a crappy parent, but a twenty-something who's about to raise another human being for 18 years is under a bit of pressure and King Lear shows what not
Perhaps the most interesting thing about King Lear, however, is the lack of Lear's wife. My high school English teacher (in that wisdom which is also a function of age) brought this up, asking us why Mrs. Lear never shows up. Is she dead? Are they divorced? Does she not care about her dysfunctional daughters? Or has she recognized that they are past the point of saving?
This is one of the better uses of negative capability in Shakespeare, making the play more of a psychological hide-and-go-seek and less of a rote senility story.