Taking your mailing list and breaking it up into segments is nothing new. It helps get a message out to a more specific group of people than would have received it if you just hit send to your whole list.
Be careful though when doing this. It’s easy to think about this practice as splitting up people based on their personalities and traits.
While there may be some overlap, it’s not the real reason someone should get a given message you’re sending.
No, the reason is the problem that you’re trying to solve for them.
Just because kids in a group are the same height doesn’t mean they all have the same needs.