Underdeveloped- A Zombie Story

This isn't your run of the mill zombie apocalypse story. Zombies are overturning cities and eating through towns but it's discovered that they would much rather snack on fully developed brains than underdeveloped brains, teens and kids being slightly safer than the adults. This causes chaos and kids and teens band together to form survival groups. But we all have to grow up sometime and in this world its not only the fight to survive but a race against time.