Water fountains are great places to find inspiration for photography experiments. Some of them have unique designs or are very utilitarian. Water and the way it reflects the sunlight is very photogenic as well. One idea is to experiment with taking pictures of a water fountain and the water from different angles. Also, find indoor and outdoor fountains to photograph.
Turn a two-liter bottle and a long drinking straw into a water fountain that illustrates the principles of air pressure. Make a straw that is long enough to reach within four inches of the bottom of the bottle and stick out of the top by a few inches. Attach one straw to another to achieve this. Fill the bottle half full of water, and hold the straw in place so that it rests in the water by a couple of inches. Use modeling clay to secure the straw to the top of the bottle. Now blow into the bottle. When you release the pressure, the extra air and some of the water will come out of the straw like a fountain.
Here's a fun experiment that requires adult supervision. Start with a 2 liter bottle about two-thirds full of soda. You'll need an extra lid for the bottle, some string and a roll of peppermints with holes in the center. Tie the end of a piece of string around one of the mints and then thread the other mints onto the string like a necklace. Pass the string through the inside of the hole of the second lid. Pull the candies up so that they fit inside the lid, and tape the string. Now take the bottle of soda to a safe place. Replace the lid with the altered lid. The candies should be above the soda. Remove the tape, dropping the candies, and get out of the way. The soda will come gushing out of the hole in the lid like a fountain.
We drink from water fountains without a second thought, and spend a lot more time and energy worrying about the cleanliness of toilets. But it's possible that the toilets at your school are cleaner than the fountains. Find out from a janitor how often the fountains are sanitized, as compared to the toilets. Now take samples of both and test for bacteria with the help of a science teacher. You'll be able to grow the bacteria and examine it. You may be surprised at what you find.