I was asked the question a little while ago "what do I do about my employees who are below average?". My answer was "Nothing! Half of your employees are below average". When we talk about performance half of anything is going to be above average and the other half below average. That is how average works.
The conversation we ended up having was twofold. First how to move the average for the group up and second who were the stragglers. And then what could be done to help raise their performance.
At the end of the project the average performance was up. Half of the employees were still below average and the over half above average just like they should be.