Hmm... You found my answer! (internal pride :P)
I'm going to argue why that question is on-topic for the site. To do this, I'll simply ask the same question as I did in my linked answer:
- Is this question about interacting with people in a specific situation?
To rephrase this in the context of your question, I'm going to change the question a little bit to this:
- Does presenting in front of an audience qualify as interacting with people?
Aah. That's better! My answer is definitely yes.
Presenting to an audience is really just interacting/lecturing/conversing in a more formal way. Often, there's only one side that does most of the talking. But you still have to worry about engaging your audience, communicating your thoughts, asking and answering questions and so much more. There is no reason to believe that the question is not about interacting with others.
So then why was it closed?
The reason that appears in the banner is that boring, generic reason that was unhelpful. We'll never know the actual motive for why it was closed. 5 people believed it was off-topic (they all voted for the same off-topic reason), but only one of them offered a reason (which itself wasn't helpful at all, and wasn't supported by any other closers):
I voted to close this because this is the kind of extremely broad question that we typically try to avoid on StackExchange.
Really? Too Broad? We have a reason called "Too Broad" for that (and please do close as Too Broad if that's what you really think). [/rant]
But in all seriousness, that's what more of our site is. Interpersonal Skills is not going to have questions that are objective, but more subjective. There are "good subjective" and "bad subjective" questions, and while I don't want to explain that right now, I feel that this is a good subjective question. Just because a question can attract different answers doesn't make it too broad - answers come from experience which can easily be argued and supported. I mean heck we have questions like this and this that have been well received as well.
Personally, I thought that this is a question we ought to have. It describes a real issue that you are facing, you've included the setting (school), issue (non-confidence in presenting), and everything that we want to see in our questions. It's a good question.
That's just my take on it though. For what it's worth, I've cast a reopen vote on that question.