I'm not saying either answer is WRONG, but here's the answer to your question: Yes, Tor ought to protect you from an admin looking at your traffic. If that's all you wanted to know, stop reading now.
HOW TOR DOES THIS:
Tor employs a principle called onion routing to ensure privacy (hence its name, The Onion Router). Here's how it works: You hook up to the Tor network. Then Tor works out a path THROUGH ITS OWN NETWORK OF COMPUTERS WITH TOR for your data to take. Here's a graphic showing a prospective path:
Now you perform something called a Diffie-Helfman key exchange (SE community, please correct me if I'm wrong about this part) with all computers along the path individually. In a 3 computer path you now have worked out
f(x) (with the first computer),
g(x) (with the second computer), and
h(x) (with the third computer). Let's call your request for information
m. You work out
f(g(h(m))) and send it to computer 1. Computer one, who only knows
f^-1(x) (meaning f-inverse of x), performs that operation, and sends the result along to computer 2. Computer 2 only knows
g^-1(x), so it performs that and... well you get it. After computer 3 has undone the third encryption, it takes a look at your request and passes it on to the pornography server you were trying to contact, named Bob. Bob sends computer 3 your erotic Animorphs fanfiction (sorry, couldn't resist). Computer 3 now sends your fanfic along the same chain of communication that we already looked at.
This system is effective for several reasons, but I'll just say this: Due to the properties of the Diffie-Helfman exchange (there's another answer on here that explains it just beautifully) your sysadmin will never see the keys for
h(). All he will see is that you're sending an encrypted packet to an IP that doesn't belong to any website at all. Will he be able to determine that you're using Tor? Almost definitely. Can he do anything about it? Well, he can stop you from accessing the internet (in fact, he might decide to), but he can't see your internet traffic, which means that you can keep your erotica to yourself. I would warn you that Tor includes an add-on called NoScript that stops you from watching video, so I hope your fanfic is in text form.