I could of course just reapply the tag (at least I expect I can.. can I? Haven't tried.), just to have it removed again.
Usually I'm happy that people mess around with "my" tags, as it improves the question. Not this time. Clicking on the editor only reveals the edit and not the reasoning. How should I proceed?
I'm not a moderator; I think this information is correct, but please feel free to edit, comment, downvote, or any combination of these if it's wrong.
In general, if you believe your question is de-tagged wrongly, here are some options at your disposal:
Read the tag's tag wiki and see what other questions are tagged with it. This can sometimes help in figuring out whether or not a tag is appropriate for your question.
Search meta, to see if the tag is under consideration for removal, or otherwise under discussion.
If removing the tag clearly was't intended by the editor, just add it back.
Similarly, if you are sure the editor removed it based on a subjective judgment, you may add it back (but don't get into an editing/rolling-back war--if it' re-removed again, use a different option). In the case of a tag that has few or no other questions, you should probably not do this, as the intention of the editor may be to get rid of the tag. That's not always right, but should usually be discussed.
This also applies to editing other people's posts. I've occasionally been guilty of re-adding removed tags to posts I've edited, not realizing that the posts had them before, and then they were removed. If I'd realized this, it would have been better for me to discuss it first!
If you do re-add a removed tag, it helps to explain the reason in your edit summary for the re-addition.
Ask a specific question on meta, about whether or not the tag should really have been removed. That's what this question was taken to be about (in comments). This is usually the best way. If in doubt, this is probably the best thing to do.
Ping the user in chat. For example, to ping me in chat, go into the general chat room, and post a short message with @EliahKagan in it. Even if the user isn't in chat, they will be notified (though it may take some time and you shouldn't expect them to reply immediately). Then you can ask them about the tag removal. You should avoid pinging repeatedly, and remember that meta is often a better place to post, because you can solicit community consensus here.
In the very unusual situation that someone is clearly making intentionally abusive edits removing tags, you can flag the post itself for moderator attention and explain the problem. Unless you're quite sure this is what's happening, it's best to ask on meta first.
If you feel very strongly about it, add it back and leave a comment explaining why you've done so, perhaps @mentioning the person who edited it out (so they can respond).
This goes for any sort of edit that you disagree with (whether you're the editor or the, urm, editee). Reverting is optional but you shouldn't do nothing if you think it is the incorrect thing to do.
Not every incident needs to go to meta. I respect that you're asking for the conduct here and not about the removal of the children tag (though I'll say something on that in a minute).
Have a word with them in comments. Talk with them in the chat rooms. Find their email in their profile and have a chat. Just remember you're not going to get anywhere unless you're polite, explain your reasoning and also listen to what they've got to say. Ignore those basic concepts and you're going to start an edit war.
If you can't come to a consensus, that's when it's time to go to meta. Be specific. People need to know the post in question and why you're opening the thread. All the moderators get a notification so even if nobody else replies, at least one of us should be able to donate $0.02 to the topic.
About children: I don't see anything wrong with the idea of having a child/infant/young-person oriented tag but I'm not wild about the name "children"... I just don't think I'd neccessarily think to add that tag if I were writing that sort of a post...
But I don't know if there's anything better. Thesaurus.com offers the following synonyms:
adolescent, anklebiter, babe, baby, bairn, bambino, brat, cherub, chick, cub, descendant, dickens, imp, infant, innocent, issue, juvenile, kid, kiddie, lamb, little angel, little darling, little doll, little one, minor, mite, moppet, neonate, nestling, newborn, nipper, nursling, offspring, preteen, progeny, pubescent, shaver, small fry, sprout, squirt, stripling, suckling, tadpole, teen, teenager, teenybopper, toddler, tot, tyke, urchin, whippersnapper, young one, youngster, youth
I find myself wishing we had more use for an anklebiter tag.
No, I think children or child is probably on the right track.
I untagged children because I felt it's a tag no one would subscribe to and was unnecessary. If you think it should be tagged with something then perhaps parental-controls would work?
[parental-controls] [education] for answers with both tags to show up. You did good asking this in meta, hope it was not much of a problem. Maybe if we saw more of these questions the automatic tag sorting trigger wouldn't be as harsh, its just how we do stuff. If needed always discuss it here.