Out of my first semester I got 3/4 H1s. Most of it (so far) is rote learning, so if you work consistently, and have a decent study plan for exams (I started studying about 3 weeks before swotvac which is one week) then it's definitely possible to get H1s. A lot of people completely bomb out in Uni after doing year 12, i don't know why but I guess they just start to get lazy after such a long holiday. I'd say most work pretty hard though, because we all want a good GPA
It's really not as hard as people say it is, not if you work at it.
It's MUCH MORE EASIER than getting a SS of 45+ I didn't even get an SS above 35. Anyway, a subject goes for 1 semester anyway, and then we start sem 2 with new subjects. (holidays are fun in that respect, no need to look over semester 1)
Edit: As golden mentioned, lectures are recorded. This helped me a hell of a lot, esp. with chemistry, often I didn't understand something at all, revisited the lecture again at home (listening to it again), and it just helped so much.
Regularly attending tutes is important, starting assignments early, attending topic tutorials (they have these for bio- v. helpful), and visiting tutors during consultation hours helps too
