I have been sleepy. Very sleepy. Even waking up tired. My children too, normally bounding out of bed at 6 am are still fast asleep at 7:20 this morning, even though they know there is banana bread for breakie.
They must be ill was my first thought. As I began to ponder this drowsiness I realized that each year it peaks just after Christmas and lasts through February. Obviously this is a response to the shortened days. I myself am very sensitive to the changing seasons. In October I become suddenly fatigued, achy, miserable. By February I have wilted like a cut flower; moody, drowsy and restless. By March I am outside gardening in a tank top as soon as the mercury climbs over 60 just to feel the warmth of the sun on my skin.
Okay, so this is natural I think. Its just our circadian rhythm (basically your bodies internal clock) telling us when to be awake and when to go asleep. After all, it is affected by things like light, it is natural that light changes in duration, so perhaps it too is natural that our sleep changes in duration in synchronicity with the available day light. I begin to research this some and discover that, circadian rhythm sleep disorders are, according to Wikipedia:
a family of sleep disorders affecting, among other things, the timing of sleep. People with circadian rhythm sleep disorders are unable to sleep and wake at the times required for normal work, school, and social needs. They are generally able to get enough sleep if allowed to sleep and wake at the times dictated by their body clocks.
What? Doing what your body does naturally is labeled a disorder? Really? Who determines these "normal" times that one must awaken for school, work and social needs? Even more compelling is that Czeisler et al. at Harvard found the range for normal, healthy adults of all ages to be quite narrow: 24 hours and 11 minutes ± 16 minutes. The "clock" resets itself daily to the 24-hour cycle of the Earth's rotation. Yet we have determined it best to trim the time from each day and add an extra day every 4 years. The bigger question is this: what is it that makes us impose rigid schedules on our bodies that are in tuned to the clock of nature? What is it within us that causes us to crave unnatural "cookie cutter days"?
What exactly would happen if I indulged our disorder natural sleep patterns? Would this impact our health? Studies have shown already that a disruption in circadian rhythms impact our cardiovascular and renal health. 
What about behavior? Could following one's natural sleep patterns positively impact behavior? Perhaps there is merit to experimenting with this, in the name of homeschool science, of course.
 Charles A. Czeisler MD, PhD (1999). "Human Biological Clock Set Back an Hour"
 Martino, T.A.; Oudit, G.Y.; Herzenberg, A.M.; et al. (May 2008). "Circadian rhythm disorganization produces profound cardiovascular and renal disease in hamsters". American Journal of Physiology. Regulatory, Integrative and Comparative Physiology 294 (5): R1675–83.