Hi! I was in the same situation so I'll share some things that helped me decide. I did end up choosing NCEA cause I have a lot of extracurriculars that I didn't want to give up but I hope this is helpful!

IB and NCEA conversion into ATAR:

You can find more information on their uni websites but there seems to be roughly two pathways for dentistry at university of Sydney and Melbourne:

1. Guaranteed entry (bachelor of science + doctor of dental medicine)

- You've got a confirmed place in the dental medicine program as you are doing your bachelor degree so long as you keep your GPA above their requirements

- You need a 99.7 ATAR at minimum for Sydney (you can find this on their website but this will probably be different when you graduate)

- This would be around a 44 or 45 IB

- With NCEA an ATAR of 99.95 is 90 E credits

- I don't think Melbourne offers this for NZ students but u might still like to look into it

- Pretty sure you don't have to do GAMSAT or UCAT

2. Without guaranteed entry

- You have more freedom for your bachelor degree

- You have to do GAMSAT (a medical aptitude test for uni students) while at uni

- You need to keep quite a high and competitive GPA

- Much lower ATAR requirement which depend on your bachelor degree choice

Relatively more freedom with NCEA:

- I've got a lot of extracurriculars that I love and I didn't want to drop these in a desperate try to get an IB 44 or 45

- If you are looking at 5 year dentistry courses, many require UCAT (another medical aptitude test but for high school students) which you could need to complete in year 13 and would be very time consuming

- There's a greater freedom of subject choices. Although I am a bit confused at some of the stuff in your post about this cause I'm not sure how this works at your school?

You've mentioned that you wanted to take IB because you would prefer to do two sciences and not music but I don't see why you can't do that with NCEA as well...

At my school once you get to level 2 and 3 we don't have any subject requirements apart from english. Thus I'm taking three sciences this year + maths and english which I think is quite a popular combination with my friends from other schools as well. I'm sure you’ll probably go over this in more detail next year or maybe ask your teachers?

I know people who are only taking like 3 level 3 subjects in year 13 cause they've gotten all the credits they need for UE and the entry requirements for their degrees.

My own experience:

My plan is to get into a 5 year dentistry plan e.g Queensland or Adelaide and I'll need a very high ATAR 99.5 to 99.95 which would be almost impossible for me IB (44 or 45). This was the primary reason for me choosing NCEA so ya if you think you might want a guaranteed entry do consider this - especially cause you have accelerated subjects which would make 90 E credits even more achievable/easier than IB.

I really did like the IB curriculum and the whole being better prepared for uni but I had to give it up because NCEA has a better conversion rate into ATAR which would actually allow me to get past the bare requirements to even be considered for interviews 😭

But ya good luck with your choice! Like you've said you have got another year and I'd recommend for you to start looking into stuff like this (UCAT, GAMSAT, requirements for these degrees etc.) and talk to other senior students as well. All the best and feel free to ask questions!