So when my laptop was in stand by and I left it alone unattended my little brother started playing around with and took out the battery while it was on and ever since then it hasn't worked. Does that usually completely break a battery.

Does it work with the power cord connected and no battery?

For all you know, your little brother may have shorted the battery with a paperclip or whatever, so the battery may be dead. The computer should be OK though.

The computer works fine with the power cord plugged in with or without the battery in but is it possible that maybe its not the batter and the computer just can't charge it anymore. The little charging light on the computer goes on and when in windows it says that the battery is charging but it never does because the second the power cable is unplugged the is no power going into the laptop.

I agree with Nodsu. Sounds like the battery is dead. Have you had it tested? If possible, take the laptop to a battery shop (Batteries Plus, etc.) and have them put a new battery in to see if it will stay on while it is unplugged.
Good luck.