My school has metal detectors that we have to walk through before we go into the school. Like the airport security-type ones. Are those harmful to my babies? Because there are pregnant girls at my school that still go through them and I've heard reports that the metal detectors give off small amounts of radiation.

The amount of radiation given off by these devices is way too small to cause damage. there is no more risk than using a microwave oven (even though this is a different part of the ionising radiation spectrum). You can safely pass through them, if there were a risk then they would either not be able to have them in airports or there would have to be special precautions for pregnant women just like they do in the emergency room for the x-ray room. :~)

(oops submitted before I had finished)

So to clarify, although they do emit radiation, it is non-ionising which means it is safe and does not damage tissues.