Learn Turkish: Bu çocuk bir öğrenci. - This child is a student.

To ask "Who is this child?", you just replace the answer (bir öğrenci) with the question word kim. The question becomes Bu çocuk kim? Notice how the word order stays exactly the same!

If I want to ask what the child is (like their status or job), do I use 'kim' or 'ne'?

When asking about a person's job or status, you use ne (what). To ask "What is this child?", you would say Bu çocuk ne? You only use kim (who) when you want to know their specific identity or name.

Where is the word for "is" in this sentence?

In simple Turkish sentences, there is no separate word for "is", "am", or "are". Just placing the subject (Bu çocuk) next to the description (bir öğrenci) is enough to mean "This child is a student."

Do I always have to use 'bir' (a/an) when stating someone's status?

No, you can actually leave it out. You will often hear sentences like Bu çocuk öğrenci. Including bir is completely fine, but dropping it is very common in Turkish when stating someone's role or profession.