You are implying by your response that these students aren't using the technology to communicate the classroom topic. Rather than having to "hide" under their desks, the typically high school or middle school students using SMS should be *encouraged* to learn the proper uses of new technology.

Of course, with our crippled public school system (another topic entirely), kicking out kids who fail is difficult or impossible.

I would put some responsibility on these 10+ year old kids - pay attention or you might get the boot. If SMS helps you stay on-topic and enhance the conversation with your fellow students, that should be encouraged.

People in the business world multi-task meetings via email and SMS frequently, and there is no reason that high school kids can't be brought into the modern era.