Don't teenagers need to learn to get up early to prepare for the "real world"?  Or, why can't they just go to bed earlier?

Sleep is a need, not a luxury; the only thing a lack of sleep prepares you for is to function below your potential. Asking a teenager to suffer sleep deprivation now in order to prepare for the real world is like asking a toddler to give up his nap in order to prepare for Kindergarten. 

Going to bed earlier is not a solution. Adolescents need about 8.5-9.5 hours of sleep a night, which is more than adults need. In addition, their sleep cycle shifts about two hours later, so that they have trouble falling asleep before 11 p.m. These changes occur in all human adolescents (and many other mammals) and are temporary. When they are adults in the real world, their sleep patterns will be adult sleep patterns. It is not coddling to allow a teenager to get enough sleep any more than it is coddling to allow them to get enough to eat.

Even universities have started to push class start times back. It is hard to do a randomized control study of the impact of start times - most high schools can't have half the kids start at 7:30 and the other at 8:30. But the US Air Force Academy did it and researchers found that the first year students who started after 8 performed better not just in the morning but all day:

"Results show that starting the school day 50 minutes later has a significant positive effect on student achievement, which is roughly equivalent to raising teacher quality by one standard deviation."