This is why the ground offensive is far superior to air attacks. You shouldn't bomb a school just because military is near/around it. You should send in your paramilitary and remove the military you are fighting without harming civilians/children.
Sorry, you can't blanket all bombings with "terrorist were there" bullshit. Its Gaza, tiny as area with way too many people already. One of the most densely populated areas in the world. Hamas' military wing is in every building technically, they have no where else to be located.
If Israel expects to finish off Hamas they won't do it by killing kids. Just as Hamas won't get Israel to leave Palestinian territories by firing rockets. Same thing.