Why does the school swimming pool have static electricity in it?

Answer 1

That may not be static electricity! Contact your local health dept and the school administration concerning this problem. The health dept needs to perform tests to determine the source of the electricity and have it corrected. Act NOW !

Answer 2

Water does conduct electricity. Everything conducts electricity, at a high enough voltage. Air is normally a pretty good insulator, but you'll notice that doesn't stop lightning, where the voltage can be in the hundreds of millions of volts.

However, absolutely pure water doesn't conduct electricity very well. Adding even a small amount of contaminants, though, makes it a much better conductor. Pool water (or sea water, or even just tap water) contains dissolved minerals that allow it to conduct much better (at much lower voltages) than pure water does.