I've had some experience with using interns in test groups over the past eight years. What I want to do is present two cases - one that worked poorly and one that is working well - and then draw a few test-group-specific conclusions.
This summer we've had two interns in my test group. There are several good engineering schools here in the New England area, and they run programs that send students out for an entire semester. The firms get good yet inexpensive help and the students get college credit. We had an intern in our group last year and he worked out well.
One of our interns (call him John) was tasked to work with me on a couple of different projects I have. John is an EE major who has interned with two other companies in the area (with a good track record) and has excellent grades in school. He's a nice, easy-going guy, fairly responsible for his age, and very eager to work with some serious technology.
I have two major projects I am managing. Both projects involve wafer-level testing, although the second is more software-oriented than the first. The first thing I did was make a general plan of what I'd like him to do. First he needed to learn the basics of the test stations and then get some practice time in. Since most of the first project can be viewed as separate mini-projects, I decided that I could parcel out some of that work to John.
I forwarded a collection of documents - work instructions and a couple of presentations I had made for the stations - for him to read. I spent time showing him how the testing worked. Before I went on vacation for a week I asked a production engineer to help him do some testing by himself, and I forwarded detailed instructions of some work he could do.
When I got back from vacation I was pleasantly surprised to see that he had spent most of his spare time in the clean room working on the tasks I had assigned. He had not completed them, but he showed me how far he had gotten and had clear plans for what remained. Since that time I have assigned him other small projects with clear instructions, and he has completed them successfully.
Part 1 of 3 talked about a unsuccessful intern.
Part 3 of 3 will draw a few conclusions.