The curriculum will just become more fragmented as these issues continue to prop up. Private schools might be the right way to go, but there are very few around, and that also tends to segregate people, which is kind of counter-intuitive to 'multiculturalism'. As far as I remember, music and phys-ed were mandatory only for the first 2-3 years and then they become optional toward the end of secondary school.
In elementary schools - who really cares? Grading isn't as stringent and music and phys-ed are synonymous with singing, humming a tune, maybe playing a bit of recorder and having recess. And even then, the kids are barely conscious in the classroom so it's really nothing to get your panties in a bunch about is it?
I think muslims should just let this go at the elementary level as it doesn't really pose a threat to their religious values. Secondary school is where the curriculum becomes multi-faceted, and that's where they can have the option to take music or phys-ed or drop it if they want to.
Also, our national anthem, is a terrible terrible song that shouldn't be forced upon anyone at any age.