why do they school up?

[2013skiff]

why do they school up this time of the year and what makes them decide when its time to school up?...thanks

[piper]

My uneducated guess (from research) They are a nomadic type of fish, constantly on the move. They typically stay in small groups anyway. My guess is this time of year will begin a transition into fall feeding. I would think of it like cowboys herding cattle...strength in numbers. I would also think that as the water cools a pack will maintain a better body temperature as well.

Stolen from a  website...google is your friend  

Most striped bass travel in large schools, except for the very large fish, which travel in solitary. For the first two years of life, striped bass live in small groups and are often called "schoolies." Female fish grow larger than males and are referred to as "cows."