In reply to Hans:
It might be helpful to know why they're learning navigation; is it for practical use in the outdoors (e.g. DofE), or is it for academic purposes?
I think that, by year 9, most kids have already acquired most of the mental tools they need for outdoor navigation, only they don't realise it. So my introduction would be to ask them the different ways in which they find their way around school, and around town (e.g. giving instructions to a stranger). This will bring up many of the techniques:
by landmark (topographic) - 'go through the first door, then go as far as the water cooler, then go up the stairs'
by junction tree (topologic) - 'take the 2nd left turning'
by distance/bearing - compass & ruler, left/right/straight on & pace counting
by following signs - fire exit, road signs
by breadcrumb trail - e.g. paper chase games
by leading - 'follow me'
Pick some points in the school, break them into teams and have them create instructions based on the different techniques. Then get them to use each others' instructions.
Then get them to relate these techniques to the outdoors.
That's one hour filled...