hi,
i go to a selective (but not a religious) school in newcastle.
sor1 is an option like any other hsc course but sor2 isn't offered.
we have 2 small classes doing sor1, with a total of maybe 25 students. there are about 180 students in our year. so it's not stacks popular. but i love it, it's so interesting. i'm a Christian but we're not doing Christianity. last year one class did Islam and they're now doing Buddhism and Islam (i think) and the other class did Buddhism last year but this year they're doing Judaism and Islam. so the teachers are trying to show us some diversity in religion, learning about things we're less likely to know about, and obviously they have to teach what they have the resources for and whatever. i think it's really good to learn about what other people believe because it just opens your eyes so much. it's good for improving tolerance - helps you to say, well, i don't agree with what these people believe, but i respect their right to believe it - and i think the more people can say that, the less stupid hatred and fighting there will be in the world. it's also good to learn what religions really say because you're less likely to believe stereotypes presented by the media.
most people in our classes are reasonably motivated, but then we're a selective school, so people are like that anyway and i don't know how much it has to do with the religions we're studying.
so to answer your question, yes i think a choice would improve motivation, but you have to be careful not to choose something really hard - the school has to be able to deliver it well. e.g. the school could say we're doing Christianity and we will offer Judaism or Buddhism but not all 4 - take a vote. or stream the classes based on choices. whatever. but i don't know how motivated everyone is to start with so i can't tell you whether i think this would be a bit helpful or a lot helpful.
maybe if you're really passionate about this you could take it up with your teacher, head teacher, src, year advisor, or someone? you could go and talk to people in your class, see if they would try harder for a subject that interested them more, then suggest to your head teacher that next year there could be a limited choice and this would improve motivation? teachers like improved motivation, it means a more interested class, and better marks, which makes them look better as well as making teaching a compulsory subject less boring/painful. sorry this is so long. good luck anyway.