I'd say let's take practical-business-relevance out of it (even though I'd argue the relevance of Java, Python, and Ruby to be plenty comparable to .NET).

We're talking about high school students, not trade-school students. I think the curriculum ought to be about opening their eyes to this really incredible world of solving problems with computers and logic. I also think a bit part of the key to that is to make sure we don't saddle them with skills that can't afford to develop. You know how bummed I was after taking AutoCad or using Photoshop in high school only to find out that I'd have to mow lawns until I was thirty to afford to use them at home? That's just stupid, and spirit-breaking for interested kids that don't have 800$ (or whatever) for Visual-Studio-Enterprise-Resume-Edition.