You learn about conditional probabilities and how to calculate around those. They teach Bayes theorem but doesn't use that name or the formula, since the formula is too hard for kids to read, but you are given the intuitive explanation for how conditional events are related to each other and you write those out in event trees where it is easy to see. I clearly remember getting taught the exact equivalent to Bayes theorem in middle school, they just didn't call it that.

If anyone who learned that sees Bayes theorem later it is intuitively obvious, so there is really no need to bring it up, and there is no reason to take a course to understand Bayes theorem later as an adult. Those things are easy thanks to what you learned in middle school.