We all require adequate sleep every night if we wish to have good concentration throughout the day. It is generally recommended that
2 year olds need 13 hours,
3 year olds need 12 hours,
5 year olds need 11 hours,
9 year olds need 10 hours
14 year olds need 9 hours
The rest of us all need approximately 8 hours.
This varies as some children do better with more sleep and others need less sleep than their peers.