Considering that MY school has no hot water, then yes. Fortunately we do have heating though. Yes. In every school that I have taught in for the last 29 years most do not have hot water for students...
Yes. The water going to your school comes out of a "tap," which is an open/closed valve. In a house, this is usually a faucet though the valve you turn on to get water from the house is also a tap....
You could Boil it in a pan? Boil salt water and there should be a line of white on the side of the pan when the water has completely evaporated. You could taste it? The salt water should taste...