Haha, you sound like me when I was in high school — that’s about how much I slept in on the weekends, though I probably got more than 4.5 or 5 per night.
Most scientific authorities believe that teenagers need 9 or 10 hours of sleep a night (though one study suggests seven is enough.) (Rambam said 8 hours is the right amount, but I’m not sure if he differentiated by age.)
Studies have pointed to one reason why they get so much less than they should: the school schedule doesn’t match teens’ biological cycle. Most teens would prefer staying up late and sleeping in late, and there seems to be a biological basis for that. What happens in practice is that they stay up late and then have to wake up early for school, leaving them sleep-deprived and grumpy (making it harder to perform well in school).
Nowadays that applies to tons of adults too, especially now that devices like smartphones have become addictive distractions. Rachmana litzlan.
If most people (teens or adults) would make sure they get at least 7 or 8 hours of sleep, they’d be in a better mood, do better in school or at work, get along with others better, get sick less often and recover more quickly, and have greater self-control (“executive function” in cognitive science terms.) The problem is, it takes self-control to start sleeping more to begin with!