This is the exact use case for setting up a domain. I would HIGHLY recommend you do so. You'll be a much happier and saner admin when you do.
I take that back, since the students do own the laptops forcing them on the domain isn't such a good idea.
What I would do in your situation is this:
In the image setup a common admin UN/PW combo so that they all have a common admin account coming from the factory. Then, when you distribute the machines - and this is where it could get sticky as far as manpower - give a class on basic administration. Things like:
- How to change the admin password
- How to create your own limited account - and why it is a good reason to use that day to day
- How to setup file sharing
- How to access the school's student resources from the laptop
- Depending on the age of the students - where to get free development tools
- Visual studio express
I would also talk to some of the more tech savvy students to see if they would be willing to volunteer time after school to help other students - basic tech support, re-image as needed, general help. Not only does that take some of the work load off you - but gives the students something to put on their resume / college applications if they choose to go into IT (or preferably go to college THEN into IT)
To address the control comment, just because they are on a domain doesn't mean you can't make the students group power users or local admins. In fact it would let you only set that on certain machines - so you could have a set they couldn't mess up.
For the user creation on login - you'd have to write some sort of hook into MSGINA i think - i've been out of education tech too long to know if that exists.
In any case, I would suggestion you look into something like deep freeze to prevent the machines from getting tooo messed up.