When I read stories like this, I actually want to call up the author and verbally berate them. Evidently, someone decided to look at a large group of school children and see if there was a correlation between math test scores and birth dates. Not a particular correlation, mind you. There was no hypothesis. They weren't looking for a particular pattern, just any relationship would do. Shockingly, they were able to find one. In this case, it's that summer birthdays lead to poor performance, and they actually attempt to pin the blame on pesticides used during this season.
I don't know how many times studies like this have to be shot down before people get it. If you look at a random group of people, some people will do better and some will do worse. That's what randomness requires. We would not expect those good and bad scores to be evenly distributed. They're going to clump up in some months. But they could easily clump up in different months with different samples. Unless you are looking for something in particular to back up a hypothesis, you aren't doing science.
I don't have to know when this journalist was born to know that they don't no a thing about math. They've proved my hypothesis for me.