Did you ever work for someone who seemed to have one set of standards for you, and another for someone else? How easy was it to please them? How did it make you feel?
While we do need to act in flexible ways leading others, since each person is different, we owe it to the team to hold to our standards. Performance standards may be variable as a team member matures (they may be expected to do less when they are new to the team and progress in a reasonable manner to the top standard) but they should be consistent. When they stop being consistent who do you think notices on your team? Everyone.
If you suddenly change standards don't expect people to like it.
People need to know the reasons for things. Suddenly requiring everyone on the team to do more isn't magic - people either embrace the standard or resist it - and when the change is too sudden or unreasonable the only sensible choice is to resist it. As leaders, that's not what we want.
Instead, we should explain the reasons for any change in standards. We should calibrate carefully how much of a change is immediately possible and how much should be gradually implemented. We shouldn't surprise our people with what they perceive to be harsh implementation. That seldom works.
Yes, it's likely that as a leader you will sometimes need to raise the standards. Do it with care. Determine reasonable standards, implement them carefully, and communicate constantly - it's all part of high performance leadership.
How do your people feel about your performance standards?
-- Doug Smith
Front Range Leadership: Training Supervisors for Success
doug smith training: how to achieve your goals