On the homeschooling group I belong to, the question keeps coming up, What is "unschooling"? It is one of those terms that you get so familiar with that you forget that it might mean something else to other people. Unschooling is not just letting your kids run wild, with no attention to their education. It is simply a rejection of the idea that when kids turn 5, they suddenly have to learn in a structured way, from textbooks and worksheets - even thought they have just spent 5 years learning massive amounts guided by their interests and encouraged by their parents. Unschooling seems to work best for kids who are strongly self-directed and have a good idea of what they want to learn about, especially artistic or musical kids.
Unschooling is unstructured, child-led learning, where the child explores whatever is of interest to him or her, assisted by the parent. The idea is that a child will learn best when interested, and that by following any one interest thoroughly (especially with a little help and guidance from a parent), the child will eventually cover all relevant topics. For instance, a love of music would obviously cover music, but also could include dance, music history, the mathematics of music (which could lead to studying ancient Greece or geometry), world cultures and religions, the technology of making or recording music (electronics), computer-aided music (programming), making instruments, the physics of music and sound, and undoubtedly many other things I haven’t thought of.
Disclaimer: I love the idea, but don't have the focus for unschooling. Without some structure, I would be likely to get caught up in my own projects and forget to encourage my kids to widen their areas of inquiry to include the rest of the topics. Most of the unschoolers I know have one or two kids, which may explain something; I am sure that there are large families who unschool, but it seems better suited to small families where the parent doesn't get pulled in too many directions while helping the kids. I do use the some of the ideas within my structure, and try to incorporate them whenever I find a place for them.