I feel that the government, national and state, should take a stand in this dilemma and develop a campaign to try to solve it. Conversely, adults have the same problem. Some adults do not bother to go that extra little step to save water, but rather they use more water because of the simple fact that it is easier. A few ways I believe we can get high school students to conserve water is by taking them to a water plant, put them in a simulation of were they have to ay the water bills and deal with the ongoing water problem in the future, and you could show them a projection of what life would essentially be like in 200 years when all of the ground water is used up and we have to find different methods to gather rain water.
One thing that you could do to help kids understand just how complex the water purification and extraction process is take them to a water plant and explain to them about it. You could tell them how water is purified and cleaned once it is extracted from the ground so they begin to grow a form of respect for water and the people who devote their lives to it. Also, you could explain how long it takes ground water to move, and how if it is all used up then it takes even longer to get water and prices sky rocket.
Another idea for getting high school students to want to conserve water is to show them just how much it is. Put them into a situation as if they were adults and they had to pay a constantly rising water bill, while their kids are asking them for a new car. Then they may realize that by conserving water and getting other people to they may gain in other aspects of their life. You may also use analogies such as, if you use a water conserving showerhead instead of a regular one then you would be able to put that money to 3 new shirts, or similar analogies that would make them want to conserve.