realistically, how much more effort would you put into re-doing it?
No more than 5 hours a week. I'll also do it through distance education, so that will leave me with more free periods to focus on other subjects.
What subject are you considering dropping in order to repeat it? If you're not planning on dropping one to repeat it I STRONGLY advise you not to do it. You would just be putting your other subjects at risk.
My school won't be offering specialist due to a lack of people wanting to do it next year. Teachers have been pressuring everyone to drop it for further but I find Further boring and tedious. if i repeat bio i will do 6 subjects because i don't want to lose an increment.
EDIT: Just to check, you can't get two study scores for a particular subject if you repeat the same subject, right?