If our children are being taught that tattling is bad then when do we teach them to be good citizens?

My son's teacher had a lesson today that said tattling was bad and we should not do it. As a five year old he believes that now. I have always told him to speak up and get help when needed. If we are now being taught that that is wrong, when do we teach intervention and good citizenship? I do not see a difference between a child standing on top of the slide's canopy (about 12 feet off the ground) and an adult standing on the ledge of a building. Both can be very dangerous and ens up with someone getting hurt. According to the teacher a child should not tattle on the other child for doing something dangerous. Wow. Should we not report crimes or abuse because that is tattling and none of our business.... I just don't get the way kids are being taught nowadays. In my experience it is the neighborhoods with the most "tattlers" (neighborhood watch groups) that are the safest. Again where do we draw the line?