Do people need to sleep

Now, sleep is a big problem for me, because I went to sleep late and woke up early which means my sleep is unsufficient.Recently, I can't concentrate in the class or in the worst case, I fall asleep. During this week, I was preparing for PSAT, and I slept late in order to study and remember vocabulary as many as I can. Conversely, I got the worse result. For instance, my memory getting badly, and it hard for me to remember new vocabulary, I even forgot some previous vocabulary. I am unable to focus on classes or homework assignments, after school, I feel I want to sleep but I have to go basketball practice. As this accumulation, I am easy to get tired and distracted. Even though I still confused if I should spend more time to study or not, the certain thing to know is, I should get more sleep. In this way, I think I can get better job on my work, therefore, I determined to sleep earlier in order to get concentrate and strength.