Petite Chez Scheme from Cadence Research Systems is a complete Scheme system that is fully compatible with Chez Scheme but uses high-speed threaded interpreter technology in place of Chez Scheme's incremental native-code compiler. The latest version is 8.4. It should be installed on the lab machines. I'm sure you'll want to install it on your own computers too, so following are instructions on how to do that.
If you follow links from scheme.com you will get to the download page. Follow the instructions for your architecture. Be very careful to download Petite Chez Scheme. You won't be allowed to download Chez Scheme without a licence (which costs money!).
Petite Chez Scheme is distributed as a self-installing executable (.exe) file for Windows of various vintages, as a tar.gz file for Linux and other supported Unix systems. There are different packages for intel-based and power-pc macs. You may need to investigate what kind of computer you have to choose the best version. For myself I chose the 32 bit Intel Mac non-threaded version: pcsv8.4-i3osx-1.pkg.tar.gz or pcsv8.4-i3osx.tar.gz: Petite Chez Scheme for Intel/AMD MacOS X. Double clicking the downloaded file created a .pkg file. Double clicking that launched the installer. You will need root (Windows: administrator) privileges to complete the installation.
You can also download the contributed Scheme Widget Library (SWL), which provides a graphical user interface and windowing/graphics library for Petite Chez Scheme. I won't be using it for this class but you might have fun with it.
I trust that petite chez scheme is available on the CS lab machines. Just type "petite" at a shell prompt to start up a scheme interaction. This can be done inside of emacs if you like (and you should!).