Pythagoras ('s school?) discovered some cool maths but the famous theorem wasn't among them.

There is concrete evidence that the Pythagorean Theorem was discovered and proven by Babylonian mathematicians 1000 years before Pythagoras was born.

Nice summation* of the history around what we call "Pythagorean Theorem":
https://link.springer.com/article/10.1057/jt.2009.16

#math #history
*that's a math joke; it's funny.