Remote GUI Login
By: Richard Glaser, University of Utah - Revised: 2007-10-30 richardIntroduction
There are times in educational or other environments, you might want to quickly login a group of Mac's like in a classroom in situations where attendee's might not be affiliated with the university and be using temporary guest accounts.
You can use Apple Remote Desktop's, Send Unix command to accomplish this task.
Send Remote GUI Login Script
Next, you want to send the following unix command to the clients using Apple Remote Desktop
osascript <<EndOfMyScript
tell application "System Events"
keystroke "username"
keystroke return
delay 3.0
keystroke "password"
delay 3.0
keystroke tab
keystroke return
keystroke return
end tell
EndOfMyScript
In the above script example, you want to replace "username" with the account name, and "password" with the account password.
The "osascript" is a command to execute AppleScripts from the command line. "System Events" is used to provide GUI scripting and enter in particular keystrokes (i.e. username & password) and the tab & return keys.
System Events is a faceless application that supplies the terminology for using a number of features in AppleScript scripts. Among these features is GUI scripting, which allows your scripts to perform some actions in applications that have no built-in scripting support. System Events, which is located in /System/Library/CoreServices, has been part of Mac OS X since version 10.1.

Once, the clients have completely logged in, you can perform other actions with Apple Remote Desktop, like copying files to the client, etc.
Lastly, I would recommend saving this script as a "Saved Task" and Apple Remote Desktop for quick access.