There is a Cisco VPN
client for Linux, but you can't download it for free. Maybe you could ask the school's IT department to download one for you?
VPNs remain an area where proprietariness abounds. There are a few open VPN methods. There's the IPSec standard, whose implementation on Linux remains a mystery to me, though I know it's possible. There's also the
OpenVPN project which uses SSL, the encryption technology used in web browsers, to build secure tunnels. I use this to build secure point-to-point connections between myself and my clients, though it's also possible, but rather more complicated, to set it up to handle multiple roaming users. It's also possible to build tunnels over SSH if you can set up an SSH connection to begin with.
Most companies and larger organizations still use proprietary solutions like Cisco's, or Microsoft PPTP. (It's possible to support PPTP on a Linux server, but it requires "tainting" the Linux kernel with the
software needed to handle Microsoft's proprietary MS-CHAP protocols. And, of course, it's not legal to use this software within the US.)
Frankly I don't understand why Cisco doesn't just distribute its clients for free; they're useless unless you're connecting to one of their VPN aggregator products.
There really isn't a "native" Linux VPN client; IPSec and OpenVPN are probably the closest in that they are freely-available and based on open standards.