I absolutely am, without a single doubt in the world. In the seventh, eighth, ninth, and tenth grade, we had a competition called Future City in my Pre-Engineering classes that required a large group of people (about twenty in the class each year) to cooperate with each to do a few things, including develop a futuristic concept that would appeal to and conceivably rectify a problem, write an essay and a presentation for it, as well as build a model showing it.
This was always a huge task for us, and when it came down to dividing up the groups, getting to work on each part of the competition's sections, I would almost always end up being the one deciding who would do what (based on my precursor knowledge of each individual's strengths and weaknesses) and I would end up being apart of the essay writing group, which I would also oversee. Every. Year. Ideally I would be in charge of coming up with the core of the essay and finishing it myself, so I was pretty much the writer, haha. Everyone else did nothing.
When it came to the other parts of the competition, I wouldn't really step in and put much effort forth unless tensions rose due to upcoming deadlines or just general arguments (in large groups like that, you're going to have conflicts at some point or another) in which case I would be one of the only ones with a head on his shoulders, forcing me to say something. That kind of thing comes up naturally nowadays in group work or otherwise.
Anyway, went off on a tangent there, sorry. In short, and not to sound conceited, but I do find myself to be a leader.