I did debating as an extra-curricular activity through high school. I would definitely recommend it, particularly if she already enjoys arguing her point.
Was it useful? For me, yes. I’m doing a law degree at the moment, and I would go as far to say that the skills practised in debating are more useful to my current studies than high school English was. Not just the public speaking aspect, although I’m sure that will come in handy later in the degree, but the process of looking at facts, discussing opposing views and coming to a convincing conclusion. In law as in debating, it’s crucial to see and understand two sides to an issue, if only to more thoroughly discredit one side.
Was it interesting or boring? Well, obviously I found it interesting, but it did sometimes depend. In earlier years of high school our whole English class would divide into teams and debate something in a standard format debate, which could be interesting or boring depending on the topics, speakers and general enthusiasm of the class. In later years of high school I did ‘inter-school’ debating, which was a lot more interesting. We did different types of debates like Point of Information (where you can interrupt the other team to ask them questions), Cross Examination (pretty self-explanatory) and Short Prep (where a ‘secret’ topic only available to teams an hour or so before the debate started). Debate topics also got more vague in later years - instead of stuff like ‘Whaling Should Be Banned’ (one of the more boring ones I can remember) you’d get things like ‘It’s The End of The World As We Know It’ (an example of a weird topic that went really well) or ‘The Heart of The Problem is a Problem of the Heart’ (wtf… this was a failure). You didn’t mention what age your daughter was, but if she likes argument and discussion she should in general find it interesting. If she is younger, a lot will depend on the teacher - in later years teams obviously have more independence.
For me it was a socially positive experience. My good friends were on my debating team and there were friendly rivalries between us and the other ‘debaters’ in our year. We’d sometimes all be allowed to skip English class to work on our debates if we had an inter-school event that evening (our English teacher was also involved in debating, so she didn’t care) and I have many fond memories of sitting around shooting the shit and flirting and teasing and arguing pointless random things with the other debaters. Perhaps I’m biased because my good friends were involved, but I would suggest that the kids who do this sort of extra-curricular activity might tend toward being more extroverted and intellectually open. There were a few ‘oddballs’ among us but even the weirdos were entertaining. On the other hand I know people from other schools who were pompous, overly serious and would work their political opinions into every debate. If you hung out with these type of people a lot, it might not be so socially beneficial.
Yes, sometimes you have to argue positions that you don’t agree with, but I think it’s a good mind exercise to do this sometimes. I’m not sure how her class works, but at my school (I’m in Australia, FWIW) the older debating students would also learn how to adjudicate the younger class debates, which is a good exercise in itself.
When you consider the public speaking, team camaradie, exposure to topic issues that might not be covered in the regular curriculum and skills of developing a logical argument that are involved in debating, it seems like a really worthwhile class to take part in. Of course she might hate it, but based on my experiences I’d recommend at least giving it a try. Many of my fonder memories of high school come from being involved with debating.