I completely agree that there is a lack of scientific understanding in the general population. That's why we need to have science communicators (what I aspire to me).
There are several problems with the current Year 12 system (referring to HSC, not IB) and I want to run through each of the problems briefly.
1. The only compulsory subject is English. The problem is that English teaches you some skills but the way it is set up, it doesn't train you to think critically (or anything very useful, for that matter) - what I want to see is a change in the Area of Study to be a completely different and random theme every year such that students cannot simply rote learn an essay with a belonging theme and adapt it in the exam. It would make it almost impossible to really make a perfect essay on the spot but it would allow those who can think critically under pressure to excel.
2. Again, with English being the only compulsory unit, it produces students that are not rounded - students that don't do mathematics, don't do science or don't do arts subjects. It allows students to remain in their comfort zone which is a deadly recipe for training yourself out of your own curiosity and critical thinking - you choose to educate yourself out of your own creativity.
3. There is no rigorous curriculum from Year 7-10 and the difficulty is practically unchanging for four years - this makes students feel too comfortable with school work and the level is understanding, I would argue, is not much higher than from where they started.
4. The curriculum does not address scientific misconceptions - for example, the idea that evolution is a random process is ludicrous. Evolution is a result of positive characteristics having a higher chance of survival and hence, higher chance of reproducing and staying in the gene pool - there is a random element but ultimately, it comes down to the survival of the fittest. Same goes for global warming - saying that global warming is not occurring is empirically wrong - enough said. Or misunderstanding a theory as 'just a guess'. If you want to see scientific misconceptions, you just need to look for protests by climate sceptics - I heard someone say "CO2 is not a pollutant, we need it to breathe".
5. The teaching of 'why this is important' is fundamental to student learning - you often hear little rats say 'why should I learn this? I'll never use it'. And when I say this, I'm not talking about 'this is used in engineering' and that's all. What I expect is students to be able to say that relativity had to be considered when firing up satellites into space because GPS systems seem immediately inaccurate due to the effect of time dilation on the systems - that's why this is important to know but I want students to be able to do this for everything they learn because everything has a use.
6. The final thing I want to see is more practical lessons in the science class room - that's what science is and that's what we need. Have a practical lesson every week/fortnight. It will show students the application of what they have learnt in the real world.
7. Religions should go through the same level of scrutiny as science (more of a problem with society in general) because they make claims that are within the bounds of scientific understanding. For example, if religions say the universe was created by 'God', their evidence should undergo the same level of scrutiny as the Big Bang theory. I would argue that it is dangerous to allow certain groups (religious groups) to be excluded from criticism - it is fine to have your beliefs but if you want to make them public, you sure as hell should expect them to be critiqued and undergo some sort of scrutiny.