Here is some great information for parents. Thank you Apple and Yahoo!
If you’re setting up a Standard/Managed account, the Parental Controls checkbox affords you the opportunity to shield your Mac — or its very young, very fearful, or very mischievous operator — from confusion and harm. This is a helpful feature to remember when you’re setting up accounts for students, young children, or easily intimidated adults. (This checkbox is available for Admin accounts, too, but turning it on produces a “Silly rabbit — this is for kids!” sort of message.)
It’s here that you can specify how many hours a day each person is allowed to use the Mac, and declare certain hours (like sleeping hours) off limits.
To begin, click Open Parental Controls at the bottom of the Users & Groups pane. Click Enable Parental Controls, if necessary. Now you should see the screen shown below:
Clever folks, those Apple programmers. They must have kids of their own.
They realize that some parents care about how many hours their kids spend in front of the Mac, and that some also care about which hours.
Just click over to the Time Limits tab inside the Parental Controlswindow to pull up all the settings offered.
How much time. In the Weekday time limits and Weekend time limits sections, turn on Limit computer use to, and then adjust the slider.
Which hours. In the Bedtime section, turn on the checkbox for either School nights or Weekend, and then set the hours of the day (or, rather, night) when the Mac is unavailable to your young account holder.
Tip: When time limits have been applied, your little rug rats can now check to see how much time they have left to goof off on the Mac before your digital iron fist slams down. When they click the menu-bar clock (where it now says the current time), a menu appears, complete with a readout that says, for example, “Parental Controls: Time Remaining 1:29.” Good parenting comes in many forms.