Both my girls are very musical and both did it as a VCE subject.

An important thing to look for is ability. If they love dancing to music, sway to songs etc then look at lessons. Nothing is worse than trying to make a tone deaf child learn an instrument.

Find out if the school has a music program. A teacher usually comes in once a week and gives lessons. This way you can try a couple instruments to see what they like. You will need to encourage practice but if they really want to learn they will practice, especially at the start. Also don't over do the practice as this can quickly make them loose their love of learning. It doesn't matter if they miss a night or two as long as they practice the other nights.