OP,
On this board you'll get a majority of parents who think children should not be subjected to classical music concerts.
I happen to disagree. In our little circle of parents whose kids frequent the same music school, free or reduced tickets to events at Strathmore and the Philharmonic are often given to students. Many of us take advantage of them.
It's a discipline at first, like many other things - a child might sit grumpily and not appreciate the first few concerts, but as the habit grows (and there are many ways of making it fun, like having a special dinner out and being allowed to stay up late on that night), then music appreciation develops and becomes a lifelong source of pleasure. The point is not to wait until they're teens and rebel at everything you suggest. A little resistance is normal at first, though.
Of course, I'm not talking about a hyperactive child who just cannot sit still, or someone who deeply hates classical music! I don't think a school routine should be regularly perturbed by late night concerts either. But a normal child who practices an instrument and goes to the occasional concert - that's as it should be