Random drug tests in school should not be encouraged in schools unless there's hard proof it stops kids taking drugs, a report by a charity says.
Their research says the tests could destroy trust between teachers and pupils, making any problems students might have harder to spot.
The report, published by the Joseph Rowntree Foundation, has called for more research into the testing.
The scheme was recently introduced at Abbey School in Faversham, Kent.
Every week 20 pupils there are randomly chosen by a computer to be tested for drugs including cannabis and ecstasy.
Early this month the head teacher Peter Walker said no pupils had yet tested positive for drugs.
He reckoned the tests were working because pupils had decided not to dabble in drugs because of the threat they could be tested.
Government backs tests
The government has given schools in England permission to test students, and the Conservatives have promised to put more money into school drug tests if they are elected into government.
Do you think drug tests in schools are a good idea? Or would it stop you trusting your teachers?
I think that they should stop the drug tests.
Ian, 14, Newcastle
What exactly is the point if you can say no? I'm sure lots of parents don't agree with their children taking the tests anyway. But then again I think it would raise some suspicions if you refused to take the test.
Hannan, 13, Birmingham
I think they're a great idea - if you're not on drugs then you've got nothing to worry about have you?
Kim, 15, Essex
I don't like it, it makes you feel like you've been put under a large barrier. I think if children are going to do drugs they will do it and that we should have the right to learn from our mistakes. It's our responsibility to say 'no!' and we will never learn to do that if we have adults butting in all the time.
Belinda, 14, Blackpool
School drugs tests do not work - say no then they let you off. Why can't they do a special test on them, instead of asking questions?
Imogen, 12, West Midlands
I think it's really stupid. The teachers obviously don't trust kids. I know a lot of people who do drugs, but what kids do in their own time is nothing to do with teachers or schools.
Kirsty, 14, Exeter
I don't know if they are a good idea because I know a lot of people who do them at weekends but nut during the week.
Sara, 14, Essex
I think that there are a variety of other ways to stop the student drug situation, this one being not good enough proof it stops kids taking drugs. At my school we have a blood hound to sniff out any drugs in student's lockers. If my teachers took part in these drug tests, I certainly wouldn't trust them anymore.
Katherine, 14, USA
If you are on drugs and you can say no to having the drugs test then you could just say no - so what's the point?
Leah, 14, Lochcarron