All teaching is done in High German and everything is written in High German. Learning it should be a priority over Swiss German which, incidentally, your kids will probably pick up much quicker than you from playing with friends. As I said earlier it is a dialect, and it varies slightly from Canton to Canton around the German speaking parts of the country. High German is the "official" language used for road signs, newspapers, communication from the authorities, etc.

I understand Swiss German but only speak High German (although have been known to have a crack at the dialect under the influence of alcohol ).