I noticed your posting on Mini Laptop Carts. I am the Vice President for Spectrum Industries and we have several carts that may work well for you. Our LT15 laptop cart is very compact and can hold 15 laptops, or up to 30 minis. It is very versatile and incredibly well constructed. To see how it is being used for this exact application see what Saugus ISD (CA) is doing with it and how they point out the features...
I will also add an image for your review. This gives you an ideal solution to manage the laptops. Plus it can be utilized for full-size laptops in the future should you have an opportunity to upgrade down the road.
If you would like any more information just let me know. I am happy to help.
SPECTRUM INDUSTRIES, INC.
If security is your only concern you could probably daisy chain the laptops with security cables. That low tech solution appears to be sufficient. A our high school in a classroom with limited space we have a cart that works very well for us. A different school purchased tiny Apple desktop computers that are interlocked with security cables.
We have two carts in our school, and they are truly worth the money. They provide a place that can secure them when school is out, they charge the batteries efficiently, and they are very durable for the students to bump into, and you do not have to worry. When you look at the cost that you are investing on the computers, the cost of the cart is minimal when you look at the versatility of the cart.
Check out this site for a very inexpensive solution (if price is one of your criteria): Metal cart
+ Plastic bins
We are using the wall-mounted storage system in classrooms where we have 1:1 netbooks (we are using Dell minis); and the cart to store/transport them. It's not as secure as a mobile cart, but the price is only about $500/cart system.
We have found that 20 laptops will charge on one circuit without issue, so we are just using powerstrips which are made for server cabinets (they have 12 ports each). You could put them on a timer or buy a switching timer made for a laptop cart - Bretford makes a timer, but they are > $300 each.