Depends on the enviroment and what skills they have to begin with. Especially if some of the invididuals are older or already have some experience (hunting, fishing, boy scouts, whatever) you would do well to use what they know already as a foundation for more "advanced" skills.

If by survival you mean mostly staying safe and sound outdoors in a temperate woodland or similar climate I'd start with a brief discussion on the basic survival equipment (knife, PSK etc.). Show the correct way of using a knife and axe. Most people have little skill in that department but it's crucial to starting a fire or building a shelter. While you're at it, demonstrate a quick way of setting up a lean-to with a poncho or tarp. Show the best way to store and organize stuff in a backpack. Discuss the clothing and footwear most appropriate for the environment. Explain the basic navigation with map, compass, sun & moon. Where to look for water, maybe some outdoor cooking. Make it fun, it's a great way for motivating people to actually get any good at it and avoid the Rambo approach.

Only then would I go into the "hardcore" emergency survival. Eg. how to survive an outdoor emergency with only the most basic gear, light a fire in rainy weather, build a snow hole or entirely improvised shelter. IMHO the basic outdoor trekking skills should always come first and the emergency techniques should follow, not the other way around.

Also emphasize the need for getting and staying fit (you won't enjoy the outdoors nor survive an emergency if you're totally out of shape), respecting nature, observing the wildlife, learning to adapt to the natural enviroment instead of sticking out like a sore thumb. Consider organizing some extra activities such as primitive archery or tracking later on. While not directly applicable to survival in most cases they may stimulate the students to become more familiar with the outdoors and do more research on their own.