Setting up a Teen Grid Region for Educational Use
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Linden Lab doesn't "clone" islands from SL to Teen SL, but there are ways to do what you want with a minimum of difficulty and fuss.
In order to manage an estate in Teen SL, you'll have to get each
adult, starting with the estate owner, background-checked and then
have their accounts transferred from (adult) SL to Teen SL. See more
about that here:
You'll want to load up the inventory of the avatars you want transferred to Teen SL to run your estate there, before they get transferred. You can create new accounts or use existing ones, but bear in mind that once they're transferred to Teen SL, they can't return to the adult side of things. So -- put copies of your builds/objects in those inventories, and as long as they're suitable for a PG environment, you can take them with you to your new teen island and recreate them there.
If you want a double of your island layout, as well, you should save your terraforming into a RAW file and then upload it to the teen island. Match the terrain settings between islands, and they'll look the same.
If you have more questions of this nature, try asking this mailing list:
Several projects have been run successfully on both SL and Teen SL, and I'm sure those educators will have advice and explanations of what they did.