VPN Initial Connection Problem

Hey everyone. I have a problem, but it may be my lack of understanding that is the cause. Ok so I attend a technical school, and needless to say there's a lot of wannabe hackers, pranksters and what not.

So from my laptop I'd like to connect to the wireless AP's around campus, but security is a concern of mine. So I'd like to use SSH to create a tunnel to the AP, and back to my house where I have an 'always on' connection. The whereabouts of my location doesn't matter, I'm doing it more just to have a secure connection to the wifi access point, from potential wireshark captures and man in the middle attacks.

My problem is thus, I want to do an ssh user@hostaddress -D 8080 from the terminal. This says create a secure connection to my user at my home address, and put all traffic through port 8080. But I can't execute this because my school has one of those "Login to use wifi" pages. Where you must supply your credentials that you are a student before any connections can be made.

So I'd have to put in my student ID and password, before I can even set up the tunnel to the wifi. This isn't just with my school, it's also at starbucks. You must supply a password to their wifi, unencrypted, before you can set up the vpn to the AP. This first initial step may seem trivial, but it's the kind of thing I want to avoid. Is there anyway to set up the vpn to the AP before having to prove my access to the login page?

If you could set up a tunnel before login, you could get free internet, so this doesn't seem likely.

I don't understand how it would make you more secure, in any case.