Congratulations to those kids and their parents who are admitted by universities, especially those admitted by the top universities like Harvard.  It is a great achievement for the kid as well as for the parent.  And thank those who share their great experiences with us.  It is a great info to me though my kids are still too young.
However, I do believe that月半婆婆asks a great question “俺老大不考哈佛了. 去哥能睡8小时觉的地方吧？ ". Other day, I also hear some high school students who got top university admission sleeps only 4 hours day.  I agree that kids have to work hard to get into a top university.   And I encourage hard working.   It is something wrong that 4 hours sleep is for preparation to get into Harvard and 4 hours sleep is to keep a good grade in Harvard.
To me, either we select a wrong school or Harvard selects a wrong student.  It is just not a good match, not a good marriage at all.  It is absolutely wrong to go to Harvard and sleep only 4 hours.
I would advise you and your high school kids not to prepare for the so-called top university if your kids have to sleep only for 4 hours a day. Or I should tell you that your kids are not talented or gifted to go to top university though you may not like what I say.   Look, Bill Clinton, my great hero is very intelligent and was a very good student, but he even takes nap every day.
Come on, it is just going to a university. It is not worthy of your valuable sleep. Sleep at least 8 hours every day and play as much as you can, and then go to a college that you feel comfortable. Look, No Worry never sleeps less than 9 hours no matter what, even now at age of 60.   Eating and sleeping are his number one or two important things that he has to do every day.  Otherwise, he just does not feel good.   He didn't go to top university in China, nor did he in America. But how many people in the whole world are no worry as No Worry is and how many people are as happy as Be Happy (No Worry’s anothoer name) is. Not many.   Please don’t call me a “ loser”.  I am not.   I guess I am doing pretty well, at least as well as you do if not better.
How to get to Harvard?  Many parents have already told so many stories.  And let me show off one time, just this time for your reference and information. My little brother went Beijing University. Bei Da is a top university in China though it is not as good as Harvard.  It is still very tough for a Chinese kid to get into, especially 20 years ago for a country boy.  Do you want to know how he studied? He slept more than 9 hours a day. He was the chief editor of his high school newspaper. He played Ping-Pong very well. He often helped his classmates with their courses.    He read so many magazines and books.  He was crazy about Lui Lan Fang’s Yui Fei and Yang Jia Jiang and Yuan Kuo Cheng’s Three Kingdoms broadcastings. He got highest scores both in liberal art subjects and natural science subjects when the high school tried to separate students into two different groups. He was the leader of the three students from his school and won the third reward in our province science contests. He got so many contest rewards including one at province level in math even after he selected liberal art in high school. He published a couple of writings in some local newspapers. And he got the highest score in our county and one of highest score students in our province that year and got admitted by Beijing University. I guess that should be the way of how you go to a top university. And my little brother did pretty much same in Beijing University as he did in high school. He is doing very well after graduation from university.
4 hours sleep is not good enough for no one even for single day, let alone for days, weeks, months and years. No wonder some of our Chinese American kids went to top universities, but only be researchers or followers, employees, not enterprisers, leaders, employers because they didn’t sleep enough. Or don't have time to sociate, or and they even don’t have a well-built and attractive body because of less sleep.
Please advise our kids to sleep more and be relaxed. 4 hours sleep is not the way of how one goes to a top university or does anything. It just does not work or it is not worthy to.  Forget about the so-called top university if you have to sleep 4 hours to do it.