Whether IELTS is required varies from program to program - and depends on your profile. You'll need to check with the university / college. Even if the university / college doesn't demand IELTS - it's possible IRCC might in order to process your study permit. For college - you can't have any scores less than 5.5. Ideally nothing less than 6. For university (bachelor level) you can't have any individual scores that are less than 6. For a Masters, no individual scores can be less than 6.5.