Hi Robin,
Wow -- this takes me back to my doctoral studies! This may be an issue of circadian biology. All animals run on a "clock" that helps them keep time of time of the day, although no animal, except hamsters, runs a true 24 hour cycle. Human sleep/wake cycles can run anywhere from 22 to 36 hours if no external time cues are provided. Strong external cues(called "zeitgebers", which translates to "time givers") include sunlight or bright light, and meals. These cues help the natural clock mechanism re-set itself on a daily basis to keep the person in sync with geologic day/night patterns.
People can be pretty much grouped into three types: morning larks, who tend to rise before dawn and get sleepy in the early evening (rare), flexible, who can easily adjust to awakening and falling asleep to different times of the day as needed (the majority of the population), and night owls (aren't sleepy until late at night and can't really wake up until late morning); this is a function of an individual's genetically determined circadian cycle.
Children, and especially teenagers, tend to be natural night owls, and this can shift in the late 20's early 30's to a more flexible pattern. But some people who appear to be night owls are actually "suffering" from a kind of circadian disorder called "delayed sleep phase disorder (DSPD)." In these individuals, it is conjectured that the area of the brain (suprachiasmatic nuclei) responsible for translating light cues into clock re-seting signals isn't as responsive to light as it is in most people. In addition, they tend to have longer sleep/wake cycles, so that they continue to go to sleep later and later at night, and consequently awaken later and later in the morning. Some rare people are so badly affected by this that it becomes disabling, in that they can't function on a normal human social schedule. People with this disorder eventually tend to adjust by taking nightshift jobs.
The question is, how to help someone like your son. One option would be to take him to a sleep specialist who has a background in circadian biology. The usual therapy for someone with this disorder, however, is basically the following:
1. Expose your son to only low levels of light from early evening until an hour before he would normally feel tired. This means no TV or computer time after late afternoon -- not because of the stimulation, but because of the amount of light they emit. If he wants to read, have him read in a dimly lit room, with just enough light to read or do homework by.
2. An hour before he would normally get sleepy, turn out the lights and put him to bed. Do NOT allow any flashlights in the room. Make it clear that he needs to lay in bed and do nothing, even if he can't fall asleep. He will eventually.
3. Wake him up one hour earlier than he would naturally awaken and make sure he gets at least 2 hours of very bright light exposure (preferably natural sunlight) first thing in the morning.
4. Do this for 2 - 3 weeks, until he can fall asleep within 15 minutes after the lights go out, and can awaken comfortably, if not naturally, within 5 - 10 minutes of being awakened.
5. Repeat this cycle by pushing back lights out and wake up time by another hour every 2 - 3 weeks until your son's clock has re-set and he is no longer entering the sleep cycle at a socially unacceptable time.
This should work, but will not be easy. I know you said that he never adjusts throughout the school year, but the trick may well lay in the very low/dim light usage in the the late afternoon/early evening. This may be tough to do until daylight's savings time ends.
Just as I finished writing this, I reread your original post and have one other thought. It is possible that you son has a type of sleep apnea. Since he falls asleep within 30 - 45 minutes of going to bed, he should still be getting a good 9.5 hrs of sleep, which should be enough for an 8 year old. If he's not breathing well through the night, however, this can affect his sleep quality to be point where he's very tired in the morning. In kids, sleep apnea can be a problem cause by allergy (stuffy nose), enlarged adenoids (again, stuffy nose, but for a different reason) or having a softer than normal pallate which collapses and cuts off or reduces air supply when he lies down. Does your son snore? If so, sleep apnea could be a real possibility (it can also be a possibility if he doesn't snore). Just to rule it out, you might consider talking to his pedriatrician about it or take him to see a pediatric otolaryngologist (ENT specialist). Depending on the opinions of these two types of doctors, a sleep study may still be needed.
I certainly wish you the best of luck! My DD went through a round of DSPD during her senior year of high school. We used the above method to get her back on track, and it worked quite well.
R.
