Of course sleep is every essential for us to function well during the day, more so sound sleep for at least 6-7 hours at night , or else you get disoriented and tend to be grouchy the whole day..

I agree, the sound sleep of 6-7 hours is must otherwise people tend to forget what they said 10 minutes earlier and start repeating their thoughts expressed couple of minutes before... in exactly same words. The quality sleep is must for keeping one fit mentally and physically. 

Besides  making you drowsy all along the day, inadequate sleep makes your behavior erratic and lose your temper for no reason. Adequate sleep has the quality of strengthening your immune system.

We can immediately see the results of sleep deprivation in small children. They become restless, irritable and very cranky and unless they have sufficient sleep their growth too can get stunted since they need double the amount of sleep we adults do .

Children need more than 12 hours of sleep for their healthy growth. For this, the parents need to maintain a suitable atmosphere in the home so that the child can sleep without any external or internal noises. Inadequate sleep makes the child cry and refusal of food. Parents who cannot think of the reason for  the child's behavior will be annoyed ,vexed and create a scene.