Does not breaking the law break the system?

The other day I was reading Unpaid internships 'breaking minimum wage law' on the BBC website and started to worry.
You see, here at Unsuitable (and our sister agency One Black Bear) we often take design and advertising students on placement, as well as kids from schools who are thinking of taking up a career in the business. We don't actively pursue them and we have no set policy on how they're treated, what they'll do or how long they'll stay.
We don't offer any sort of payment (except in the case of the B-Hive winners or those like our latest recruit, Helen, who impressed us so much in her first unpaid three weeks, we asked her to do another 6 months paid to make sure it wasn't a fluke - it wasn't and she's now on the full time pay roll).
This non-payment policy, it appears, is breaking the minimum wage law. So, what is to become of the humble placement?
Well, according to the article, you can only get away with not paying them if they're an observer and not asked to do any tasks that you'd normally pay someone to do.
When we take on an individual or team, we don't want them to just sit around looking over your shoulder and making the odd cup of tea. We want them to get involved and experience the real world and what they can expect, should they break into this industry.
And that means answering live briefs - if the ad/design was to get through, not only is it a great thrill for the originator at having their work become real but we would also pay them (or buy a gift as a reward) - it hasn't happened as yet though.
Now some of the students who come in are really keen and a pleasure to have around the place, others, well quite frankly I don't even notice them being here or them leaving. The one's who are buzzing around, asking advice and interrogating why things are done the way they are, I'm sure get more out of the experience than those who sit quietly in a corner and try to sneak out of the office at 4.30.
If we are breaking the law, we need to assess how we do this. Do we start to pay? Well, no. Not for two weeks but anything longer, yes we would and rightly so. Do we stop them working on live briefs? Can't see who would benefit from this. It creates more work for us and less reward for the student, so I can't see that happening. Or do we just put a stop to doing placements (internships)? I for one think that would be a sad, sad day for agencies and students alike.