QUOTE(dcmbarton @ Nov 15 2009, 07:04 PM)

It's a difficult one without a teacher, but as a starting point, you might find this book helpful (http://shop.whitepublishing.co.uk/index.php?_a=viewProd&productId=214) - it introduces some good projects which can be worked through alone - before each project it lists the theoretical knowledge which is expected.
I ordered this and was frankly very dismayed by its standard of presentation and content.
Other than as a thumbnail sketch of the requirements for the "own composition" part of their own (VCM) performance exams, I cannot see who it is aimed at. A fronsipiece addresses itself to children starting composition but the first few pages are taken up with a (very indifferent) exposition of the learning styles/ right and left brain activities involved in composition, which is far too wedded to rather hackneyed educational theories to be of much use to teachers and surely of little interest to children.
There is a brief introduction to each grade level chapter which as David says lists the theoretical knowledge required but goes nowhere near discussing these or suggesting ways in which their development might be built into the composition exercises. The rest of the intros show over enthusiastic use of the copied and pasted bullet point and a much repeated suggestion that we buy "Theroy Frenzy". (I haven't). This aside there is roughly a facing page of tuition for each grade level from 1 to 8. Each one gives an example of one style, one piece, one instrument - despite the fact that from G3 there are usually at least three choices of how the piece can be presented and for which instrument (eg solo plus accompaniment, piano solo or keyboard melody with chords over). There are simply not enough working exercises and learning activities in the "book" (really a spiral-bound desktop-published folder) for it to be helpful to teaching, and why if you are trying to cover composing grades 1 - 8 in fewer then 40 pages you waste 12 sides on some clumsily home-made manuscript paper I really fail to fathom....
They have refused me a refund so if anyone wants a free copy..... PM me, I will never use it!
On the other hand I have found Rhinegold's AS Composition and AS Music Literacy books rather good so far. They cast more but give you much more to work with. A bit too serious perhaps for younger children though so possibly still not what the OP is truly after.
The have-a go option seems best still!