Hehe, a not so simple question.
Answer: depends if you want to match what the school is using or not.
If it's Solaris, go to www.sun.com
and look at the Solaris 9 x86 section. They allow downloads of the iso images, so you can burn to CD and install on your laptop.
If that won't work, you'll need to seek out the 'free' alternatives. They will look and feel slightly different that what you are learning in school, but they will all perform the same functions at the basic level.
I personally prefer FreeBSD (http://www.freebsd.org
) if running a server-type system, but I would look into some form of Linux, such as RedHat (http://www.redhat.com
), Makdrake (http://www.mandrake-linux.ccom
), or Suse (http://www.suse.com
) if you want an easy-install more full-featured system for the laptop. All these OS's have free downloadable ISO' as well, or you can order a pre-made set of CD's (or even DVD's) which you can pop in and boot and install.
Then there begets the problem of remote access. Most of the OS's above have some sort of DHCP config, so that if you have a DHCP server on he local network, you should be able to plug in and get running on the network. Or, if you have a cable/DSL connection at home, likewise, though some services are a pain. If you're going to use dialup to access remote sites, you're going to have to do a little playing around with that.
However, for the meantime, your best bet would be to find a terminal program, I prefer SecureCRT, and just use Windoze for the first little bit until you're comfortable with the basics of the system and how to navigate it. The only thing more frustrating than having a system you really don't understand yet is having a system you don't understand yet and not knowing how to fix it if you break something.
Do a little research on those options, and it'll keep you busy for a while.