/Applications/Utilities/Terminal.app
Works fine: to connect to your school machine you should be using something like
ssh
username@machinename.schoolname.edu
where username is your username on the school machine. Include a "-X" flag if you need X11 applications to work on your mac (and have installed and started an X11 server on your mac, and set your DISPLAY environment variable), and add a "-c" flag if you're using a modem to connect; that ensures that the connection is compressed, which works great if your network connection is very slow.
Something like
ssh -X -c
username@machinename.schoolname.edu
for all the bells and whistles. But the basic form above should get you started.
Cheers,
Paul