Present perfect / Past?

When talking to a student about his test/essay/..., what is more common?
- You have worked hard and...
- You worked hard and...

Hmm. I would say "You worked hard on that essay", unless perhaps we were talking immediately after the essay was finished or handed in. In that case, I think they're interchangeable.

- Kef

If you think the essay may need revising, or is unfinished, you would probably use the perfect form.

Also, if you want to focus on result, the present perfect would probably the "right" choice.