Mine is sort of inconsistent, but here's the pattern:
Sometimes 3-4 hours a day for several weeks. School days or no school days, but usually gets the waking times right.
Sometimes over 12 hours a day, usually right after not sleeping for over 24 hours, which it'll last for few days or weeks.
Sometimes randomly switching to the normal 7-9 hours cycle, except sometimes not at the right times (asleep at day, awake at night after sleeping for 7-9 hours).