I once got told by a manager that they didn't expect new hires to make big contributions in the first year. That was after I complained I was feeling very unproductive and wanted some help to speed things up. I quit after a few months because the slowness of everything around me was making me depressed. This was at a top5 website company.
But this is still something we should teach youngsters. Interns this summer started again they second-day standup with “Yesterday I installed my computer, and today I’ll finish bug 1”. Which is good until you notice that he intends to stay all night long and do more than expected, to exceed expectations. And that is how you burn out. In fact, exceeding expectations takes a lot of talent, because you need to exceed in…
Having someone try to stay all night to get work done on day 1 isn't reasonable, obviously, but I wouldn't go so far as to discourage people from trying to exceed expectations. I'd always love to tell young people that they should relax, never work more than 40 hours per week, never stay late under any circumstances, avoid on-call, and so on, but then I remember that much of my early career success came from exceeding expectations when the situation called for it. That doesn't mean everyone should be crushing it 100% of the time or sacrificing themselves for the company, obviously, but in the real world it often requires going above and beyond if you want to move up and get ahead.
Many interns have no baseline, so they're constantly in fear of getting fired. I think it's most important to set clear expectations and to provide constant, honest feedback. Once they get over the irrational fear of getting fired, they can start deciding how much, if any, additional effort they want to put in to the job. I'd be lying if I told the interns they're all guaranteed return offers, so I can't honestly tell them that they don't need to do better work than their intern peers. It's best to explain the situation as clearly as possible and let them make their own decisions.