As a grade 10 kid, a victim of bullying, one of my names was 'tattletale'. I knew that my classmates weren't supposed to trip me and shove me and call me names, so I told the teachers about them doing this. Not just once, many times. I finally gave up because the teachers weren't doing anything to stop it, but I still considered telling to be the right thing to do. I honestly believed the only people who thought being a 'tattletale' was a bad thing were bullies and other misbehavers. If you'd asked me back then if any adults were opposed to tattling, I'd have said only criminals were like that.
Apparently, I was wrong. I don't get it. How can an authority figure, who takes their position seriously, not want to be told of possible rule infractions? Sure, kids may, out of confusion or malice, report things that aren't really a problem. So what? You don't have to act on their report. If they're outright lying, that's a problem, but that's not tattling - it's lying. Tattling is informing an authority figure of a true behavior (for certain values of true, since it may depend on perspective) that you believe to be a rule infraction. And if you can trust the authority figure to have good rules and enforce them, then talking to them about rule infractions is clearly the right thing to do.
Besides, what about the kids who don't tell? 'Mike touched my private parts and I didn't want him to.' 'Jimmy's planning to bring a gun to school.' 'I think Susan's drinking too much.' 'Kyle's talking about killing himself.' 'I saw Laura beat Joanne up.' All those are potential messages you might be missing out on, if you discourage kids from talking about other kids' infractions. And the consequences of that are much worse than some minor annoyance.
Some people say that you should tell kids the difference between tattling and reporting, where tattling is stuff the authority figure doesn't want to hear and reporting is what they do want to hear. I say, don't confuse the issue just because you're sick of kids telling you that their classmates gave them a funny look or made a burping noise. Tell the kid that they're allowed to do that, if there's nothing wrong with it; or advise them on how they could resolve it on their own, if it's a personal dispute. But never discourage kids from telling you what's going on.
Remember, the research on bullying shows that teachers, despite thinking they have a good idea of what's going on in class, actually know only about 40% of what happens. Make sure you get told the remaining 60%, or you might be surprised by a suicide or other disaster.