That sadly only goes so far. There needs to be an inate ability there as well. They need to be aware of what they're doing, otherwise they don't understand what they're doing wrong. They also have to have a good attitude and actually try to learn. Attendence and basic time management is a big one as well.

These are things that are all controllable by the person, there's not much excuse. These are things you really can't train, it's on them to meet standards here.

If someone is failing in all these areas, then they just might not be a good fit for the job. There's a competitive market of people looking to get their job.