For many young workers today, the goal is to get a job. Doing the job is not part of the plan. In a fast paced world, companies need a fast exit process for employees who don't work out. Don't let new hires who eventually won't cut the mustard sit in a 40 hour orientation program and then disappoint you for 90 days before showing them the door. I would move to a one day a week orientation program. The rest of the time would be spent on the floor with several experienced workers allowing for a 10 day assessment that could result in a termination. A decision would be based on a daily assessment that determines if skill levels are achieved.
Your valued long-term employees will thank you. Lazy coworkers demoralize your dedicated staff. Working with an unproductive new hire for 90 days may lead them to believe the slower pace and sloppy work is the new norm and they my adjust their productivity accordingly.