[Always *]

I think you definitely need to talk to him about this. He doesn't sound like he's being responsible, and it's almost worse that he's educated about drug use so he probably is some how justifying that he's got it under control. He might even just do it occasionally/rarely, but that's enough to get caught and that's enough to lose a teaching career if caught and that's enough to go horribly wrong... I'm thinking about marijuana here, but I'm sure it can happen with other drugs, marijuana actually increases your risks for psychosis, it's foolish not to take the risk of having a psychotic break into consideration when using pot, just like it would be to not take such risks seriously when using MDMA, just cause it's not likely to happen and it's been ok so far doesn't make it a good idea....

Any how, yeah so in short you definitely need to start by talking to him about how uncomfortable you are, make sure you tell him about the risks and all that and why it bothers you so much. Tell him you undertand that he thinks he's got it under control but that thinking so just isn't good enough for you etc.

And then I think you should talk to him about the festival. It doesn't have to be an ultimatum (which always seems to have a degree of unfairness to it... But hey, this seems completely fair and is still technically an ultimatum so what ever). You should tell him you are not interested in being there with him if he's going to be high the whole time, it is something that clearly makes you uncomfortable and he shouldn't expect you to stand about watching him while he's high if you do not like it. If you tell him how much it bothers you that might make it better. And he might agree not to use it.

If he doesn't agree are you really willing to give up the festival though? Could you maybe just maybe go alone and meet other people there and tell him that he will not be there with you so long that's his choice. If you choose not to go then that's up to you... But it's not like he wants to, idk, ride a dirt bike while at the festival. Drugs aren't a fun little game and you are in your right to be uncomfortable with it. So don't feel guilty for standing up for it.