I was rambling on last night about something I remembered from college. (Yes! I actually learned something!) Here is how all this applies to homeschooling. Don't you like how I sound like I KNOW something about homeschooling even though I've never actually done it?
First, here's another example of a schema: the doctor's office. Most children learn very quickly a few items about the doctor's office. Even little bitty kids who don't speak in complete sentences tend to know 1. It could hurt like last time 2. I will get a sticker/treat when we are done. Each experience at the doctor's office provides more information that will be filed away in their little brain under "Doctor." Some friends of ours from church adopted a foster child they had been raising since she was 6 months old. She's 5 now, but about a week after they got her in their home they found out she had to have open heart surgery. Her schema of "Doctor" is far fuller than my children who basically know shots and stickers and toys in the waiting room. Recently a baby was born to one of their relatives and her mom thought she had prepared her daughter that this would be a happy time at the hospital, but she was traumatized nonetheless. Her schema of doctor just includes far too many unhappy things. Sadly, some children's schema of "family" is the same. But that's another post...
So working off of this schema knowlege (ooh, you can have a schema about schemas!!) unit studies make perfect sense. My child gets interested in something. I run to the library and look up all manner of books and activities on the subject and we submerse ourselves until we are sick. I KNOW that children learn this way. I used "thematic units" when I was a teacher. That's what we called them. The only difference was I told the kids what they would be interested in. When we studied fairy tales, I turned the classroom into a big castle with dragon's footprints leading the way in from the hallway. When we studied pigs, I built a pig-pen in the reading center for them to sit and read in. (I really did.)
But here's my problem with unit studies. Sweetheart was all interested in Indians and I could have dove in head first creating the best Native American unit of study you've ever seen! But within the week--she was not interested anymore! It would have been such a waste of time and energy on my part. She got what she wanted from my minimal efforts. A whole unit was not needed. Now, there have been times when she stayed on something for forever! You just cannot tell.
I still think unit studies are cool, but I will not be using them exclusively for this reason. However, this does not mean that you can't follow your children's interests. I think when children are interested in learning more, they will ask. Our job as parents, and teachers, is to provide them with the information they need. But to not go overboard or above their interest. It's a delicate balance.