Temperature controlled soldering stations are cheap now, and better in every way; I think there's really not much of a market for unregulated mains irons anymore. They are heavier, have a huge tip-grip distance, and a large diameter, and would be even harder for a kid to handle.
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It's not completely true. My first soldering iron was a JBC 14s, I still have it and still use it from time to time. It's light and compact, more easy to carry than a soldering station. It's only 14W but it has a lot of tip and can be used for most basic work in electronic. It's not really cheap, the iron itself is not too much expensive, if you got the original stand it cost like a hakko fx-888d, with a generic stand is affordable.
I think there are more other unregulated iron from other well known brand and they can be more cheap and maybe more easy to find in local stores or internet.
I think that for educational purpose even the most cheap station on ebay can be used. It's different if it must be the first tool, something who last for years, and can be looked with nostalgia one day. In this case don't hesitate to spend a little bit more, in my opinion.