Great reply, seriously.
Not a lot I can add, although to answer your question about the primary school teacher then no, I don't think they'd be breaking the law. I would find it hideously inappropriate and wouldn't expect them to keep their job for long, but then I don't feel Clarkson has broken any laws either.
Out of curiosity (and to find out whether I'd be right or wrong in my assumption above!), I looked up the actual text of the law. It's as this:
Clicky here to read the whole thing
Interestingly, although the Act is called the Racial and Religious Hatred Act 2006, it doesn't mention anything about racial stuff in there. I've no idea why, and I assume that case law now exists to back this up, but that's still very odd. Anyway, assuming it does apply, has Clarkson broken that law? I'm not so sure. Is it threatening, or intended to stir up hatred? You'd have a hard time proving that in court, I think. Again, I can only see this referring to religious stuff, so if I'm reading the .gov site wrong and there's more text here then please let me know, as I can't see it anywhere.