When you’re in charge of training someone, the only thing you can do is give them an opportunity to perform. You can show them what is required to thrive in their specific role – what they need to do, best practices, etc. – but you can’t make them do it. You can spend hours explaining the tactics of a position, but you can’t teach someone to have passion, to be curious, or to have a better work ethic. But if they don’t want to do it, or if they just don’t understand/aren’t picking it up quickly enough, you can’t force them to do what you would do. If it’s not working, eventually you will have to do something about it.
Be careful to not make an emotional decision about this. Be objective, but be kind. Are they just not doing something the way that you would do it, but they’re still getting the job done? Is their performance still acceptable? Are they making big enough strides where, even though they aren’t where you need them to be right now, they’re on their way to becoming what you need from them?
After you remove emotions and give their work an honest evaluation, talk with others who know the situation. Make sure you emphasize that they give you their true opinions about the work being completed by the person in question. It’s not about the individual. It should always be about the work and how it affects those around them. Many people are careful to criticize because they like the person they are evaluating or because they fear the other person will find out. But if they don’t let their true feelings be known, they are doing a disservice to the company and even to the individual. After all, maybe this isn’t what the individual wants. Maybe it’s not fulfilling for them and that is why they are not putting in the extra effort to learn and excel at their craft.
Ultimately, you must determine if you’ve done everything in your power (as the trainer/mentor) to help that person succeed. Do they only need to make a few adjustments or is it time to move on? Did you lead them to water? If so, it’s up to them to decide to drink…