General knowledge of the world is importantFirstly a quiz: How many kings can you name. What about wars. Tell me about the Tudors, the industrial revolution, the capital cities of Italy, Germany, Poland. What is the basic plot in a book you had to read at school. If you felt knowledgeable about all of them then I'm impressed (was that knowledge you gained at school or after); I would imagine most children wont be able to tell you much.
Next, when did you last find it useful to know this sort of stuff. If you knew no Geography, History, English literature, Biology, or Art History would you be able to cope. I certainly could, I do cope.
The other side to the coin is that these subjects will be taught but not in the same way. The teacher might set a task for every child to pick a part of history and say how daily life was different from now. Each child has the choice to pick an era they are interested in so that they are more engaged in the subject. They will come out with a memory of a few specific topics that they studied in detail.
If you combine that with the idea that after every project each child had to present it to the others then they all get taught a wide variety of topics.
It wouldn't work; the teachers aren't good enoughTrue, I don't think that you could re-train all the teachers to this method. It could still work with an independent school where the teachers know what they are getting into and want the changes.
It will produce an unbalanced curriculumMost normal subjects will be covered by projects; all depending on the interests of that particular student. The idea is to encourage children to want to learn and by letting them have more decisions you let them choose what they find interesting.
Where is art, music, drama; anything that brings creativityTwo points:
1. Creativity will be taught.
2. art, music and drama are bad at teaching creativity to the uninterested student.
Creativity is a very important skill and like any other skill it can be practiced. Edward DeBono has done a lot of work on how to teach creativity and this is how it should be done.