How to Teach Notes

[Greavo10]

Hi, I need some help in knowing which note to give to sopranos, altos and tenors. I know the major scale and notes, but I dont know which note a soprano or alto or tenor sing????
If I play the Key of Bb, which note in the Bb scale sings who?

[JoanHall]

It depends on the song.  Whichever part is singing the melody, they're basically singing one note in a chord.  You give the other parts whatever other notes will complete the chord that fits for that moment in the song.