I sympathise as i was in much the same situation. I've mentioned it a couple times before, (here is worth a look -
Re: Socialising ).
My school had this really weird kind of separation. I went to your average crummy western suburbs high-school. You had those who were going to tafe or places like VU. The large majority of people i know though went to places like RMIT, La trobe or Swinburne. So, mid-tier type places. A lot had a SNAP (a program to lower the requirements for rmit degrees, they offer to to certain schools) offers and for a lot of them with disappointing atars, it was their only decent course of action. So, a lot of my friends wound up there or at the other universities. You had some that wound up at the UoM. I was stuck in an awkward middle position though at monash. Pretty much no one i ever talked to at highschool went to monash clayton, so i was in the same situation.
There will be people in the same situation but you have to reach out to them. You cant expect everyone to come up to you. So, talk to people outside lecture theaters, especially in the first week or two. Talk to the people beside you, talk to people in your tutes and if possible join some clubs. I didnt go to any clubs and i really regret it. It was a bit intimidating, especially at monash clayton because a lot of the kids there were from good eastern suburbs schools and a lot knew other people there. They had a ready made social network, so, it was a bit hard and/or awkward to kind of break into that.
Monash caufield seems smaller than clayton, so, it might increase your chances.
If you try, you're bound to do a lot better than not trying. Worst comes to worst, you still have lots of friends from highschool, just hang around with them. Go to uni to do your work, talk to people in your classes and go home. Rinse and repeat. So, either way, it wont turn out that bad. Often its hard to find people with similar timetable gaps as well, so, its a lot harder than highschool where everyone got out at the same time for lunch.
Like i said above though, trying will give you better results than not trying at all. So, you have nothing to lose and everything to gain.
I also messaged you another thread.