its so tricky, without having the experience it is understandably hard to empathize with what would drive people to experiment with drugs, risking their health, lives and everything else. I do have experience of drug use, as being of a younger generation, drugs were very prevalent when I was growing up. It seems they are eve more so now. For me it was fascination, general boredom and happiness, coupled with enjoyable and pleasurable experiences that lead me to experiment. I don't think there is anything my mum could have done to prevent it, but I have lost friends and acquaintances through drink and drug related accidents, so I'm not for one minute minimizing the dangers. It's just imperative to take an approach that will keep lines of communication open, rather than close them. If you fear that your husband will react badly and make this difficult then it is probably best not to tell him,although this will understandably be very hard.
As for the school, it depends if there is a teacher or welfare support person you tryst, and are close enough to to disclose it without them informing the whole school. You don't want your daughter to end up with a bad reputation, but there might be someone who could give some honest support to your daughter in reguard to this. If you think the school hasn't done much on drugs education generally you could suggest it without fully disclosing the reasons why. Hopefully the school will be able to give some honest advice without scare tactics, sometimes the have drugs workers or former addicts come in to talk honestly about the realities. I always feel this is more effective than a police officer or teacher as they can be honest about the good, as well as the bad. Often kids dismiss drug advice on the basis of 'well that wasn't my experience so they're just saying that to scare me' etc, however, given your daughters experience of drugs being so bad hopefully she will be steering clear anyway.
The trust thing is hard, she will have to earn it back, but given her age (did you say she was 17?) she's at the stage of learning to take responsibility for her own safety and well being. It must be hard for you, and its got to be gradual, but it's important that she understands the transition. you have been responsible for her well being, and made decisions to reflect this all her life, but now she has to realise its not a case of sneaking around behind your back to do what she wants now, she can make her own decisions, but within them she is responsible for herself. She should be able to be honest with you about where she's going and what she's doing,even if she knows you wont approve, hopefully you can give advice and encrouragment on wise decisions, rather than continuing to make rules. I hope that makes a bit of sense. If she's younger than 17, like 15 or something, then obviously that doesn't quite apply yet as you still make the rules, but at 17 it should be about discussion. The lying is probably the most worrying thing in a way, because like you said it opens up all sorts of questions about what she's been up to in the past. I suppose the most important thing is to get the bottom of why she felt she had to lie about where she was in the first place, might you have let her go, all be it with instructions yo call you in case of emergency's, give you an address etc, if she had been honest?