When I was in kindergarten, the teacher pinned a tail on my pants, making me wear it all day because I told her something and it broke the rule not to tattletale.
I have never understood it when adults insist for children not to tell them something the child thinks the adult needs to know, all in the name of “tattling”.
In our family, when a child comes to tell me something, for example, like “Mom, he took my toy!” I will reply with, “Did you ask him to give it back to you yet?”
If he says yes (in this example), I would go and remind the child he needs to give back the toy because we are expected to do what we can to pursue peace and to respect each other.
But if he says, no, he hasn’t asked for the toy back yet, I would tell him to first try to resolve the conflict between his sibling before coming to me, like in Matthew 18:15.
I don’t ever want to discourage our children from speaking out against an injustice. I just want to encourage them to try resolving the conflict first, and then, please, come to an adult.