Exchange 2003 Novice - Help Required

Apologies if this has been asked before, I had a good look but couldn't see anything.

I have had to put our new students into active directory. We do this by making a new organizational unit for the year of entry, so in this case 2007 and then create users within. Since my NM has left, it is up to me. I copied a user from the 2006 OU and then copied all the rest. Now the problem I have is that the 2007 all belong to the 2006 group. How do I change the group they are in? Or have I done it completely the wrong way. I did have a go with CSVDE.exe but to no avail.
Can anyone help me.
I would also like to know how to put a new 2007 group with all the new students into the global address list.

Many thanks in advance.

You will have a tab in your user properites called member of. In there are all the groups that user is part of. We set the users up in the same situation, but all the pupils in 2007 are in a group called Year2007 and year2007 is part of pupils. This is the same for Year2006, 2005, 2004 etc... So then if for any reason we wanted year2007 to have a different GP or different mapped drives its easy to set up. But yeah, it should be in the member of section of your user properties.