Apple Remote Desktop
ARD is a great tool for managing a lab and group of OS Xcomputers.  You can make adjustments to local accounts, files onthe computer, install packages and observer, share or lockscreens.  It will also allow you to remotely control a computerboth PC and Mac. 

Allowing access to a client mac is set by the local System Preferencesfound under the "Sharing" pane.  Different access rights can beconfigured for different users for security of the client.  Tocontrol a PC client, you need to know the IP address and have the enduser set the password on VNC for your access.

Installing packages can be a useful way of updating software,installing programs or security updates.  You can install morethan one package at a time. 
The Copy Items function is often used to send out folders or files toclient computer that each user will need local access to.  Someprograms can be installed this way, too.

Sharing screens is great in a lab where the teacher wants to have astudent show their work or demonstrate a process for the other stationsto see.  What is on their screen will show up on all the otherclients.

There are many more advanced Unix scripts or commands that can be sentto the clients to update them and enhance what you can do with theGUI.  Below is an attached Text file with some great scripts touse on your client computers. 

Local login to remote computers
script to send with ARD to clients
ARD Tutorials
Video clips and resources for using ARD 3 
Using Automator with ARD 3 -advanced
Tips and guides on starting with Automator in 10.4 and ARD 3  
Install ARD 2 on Intel Macs
You'll need this tip to install Apple Remote Desktop Administration on an Intel Mac
Shortname needs to be 8 characters or less
When copying files from an admin station you may run in to problems.  
Backing up your admin database ARD 2
If you have created a long list of computers and rooms, you  might want to back it up.