I have a powershell script which does most of the command line and scheduled task work for you. It it commented to self-explain what it does mostly.
Filename: set-logoff-time.ps1
Otherwise use the guide below / copy and paste the command line examples given, again change username/time to suit your requirements.
Open the commaand prompt as Administrator, powershell can work but may not recognize multi-string days using ";".
Replace username "kids" with whatever username is desired.
Day format is, Su, M, T, W, Th, F, Sa
uses 12 hour clock, not 24 hour clock.
net user kids /time:M-Su,10am-10pm
net user kids /time:ALL
net user kids /time:
net user kids /time:Sa-Su,8am-9pm;M-F,4pm-9pm
Scheduled task, set a time. Action: Program, "shutdown", Parameters/Arguments: "/l /f" (no quote marks).