Yeah I did?
I think that's a big issue if you didn't or others didn't, which falls on the teachers / school. Or maybe the syllabus... I don't know because I was taught a lot of what is in the HSC and prelim courses in my junior years.
For maths especially, I cannot imagine a year 7 kid jumping to year 10. I know a lot of topics are repeated in a way... but that helped a lot because the basics of math became common knowledge.
We were balancing equations in year 10. Proper essay writing was taught in English in year 9.
However I was in top classes all through HS at an average school. I've heard that my school focuses on the top class and doesn't try as hard with the lower classes (I have a sibling in bottom class). And because I was in top classes, we got the good teachers who wanted to teach "high achievers". Not the crap ones that don't care.
Primary school needs a bit of a revamp as well I think. I went in to highschool with only the skills of reading + basic grammar + basic basic maths. I was taught addition and subtraction etc. then they tried teaching us long division in year 6... I've never once used long division in HS. I think they could do learning the basics of algebra at least in primary.
I go to a top 5 selective school though. So technically we should be doing something right. But for some reason Year 7-10 was not one of them.
Math can definitely be compressed. (Keep in mind I was taught the 5.3 syllabus, I have no idea what the others might entail) I mean, to put it into perspective, most tutoring colleges start in Yr 9 (2 years later than HS) and finish the syllabus one and a bit years early. That's 3 hours a week (or less) compared to the average 5.5 hours a week in school (comparing this to 2u math). Further, if stuff needs to be repeated ad nauseam because students are forgetting, then there's an issue with how it's being taught. Or the order it's being taught.
Personally speaking, the same concepts in science were repeated throughout Year 7, 8, 9 and 10. In Year 11, we literally went through the basics all again in the first term before we proceeded with the rest of the syllabus. Grappling with stuff like 'balancing equations' is really not that hard. Especially if we've already learnt algebra in maths. Grappling with concepts like moles, on the other hand, is quite a bit harder and if we were taught that earlier... imagine what we could be learning now. (coughrealsciencecough)
As for English, I know most people start learning essays in yr 9/10- which is quite a bit earlier than my school taught us- fine. But what about Year 7/8? That's still some useless years that can be shaved off.
All in all, really believe in a need to restructure the 7-10 syllabus. It might be that my teachers were just crap, but I don't think they could all simultaneously be crap until the senior years and suddenly make a 180 turn and be great.
TBH, I relied on primary school-skills until Year 9/10-ish. Primary was taught rather well for me, but I went to OC and I reckon that helped heaps. ( I remember prior to that I was always reading in class because school taught at such a slow pace that the top kids didn't bother to listen) Long division is taught so you understand how to divide without using a calculator. Personally I'm surprised you've never used it in any mathematics competition.
//end rant