Some really good advice on here, I just wanted to add my 2 cents:
I posted some tips for you, also, for the leash pulling tugging, that's a way for the dog to try and control the situation, if you're in charge they don't do it cause when you tell them EH! EH!! and stare them in the eye and tell them to knock it off in a very low tone, they do,
but, they put their scent on it, when they do this they go back to it they know it's chewed on before so it is safe to do so, so try and clean the scent off, then put something they don't like, find something, grapefruit juice, lemon, tabasco, chinese hot oil, why? it causes the leash to correct your dog, so they know it taste nasty. Watch for your dog to grab it's leash, tell them EH! EH! as they start to. Be proactive, not reactive. Because then it becomes tug. You can teach drop it but I have had some do this and come to me because now the dog grabs the leash to get a treat, they know when they do the owner says drop and they get a treat, they grab it again owner does it again. Same as barking, but that's a diff thread..LOL
Some dogs are too smart for their own good..LOL
As a leader (if your dog sees you as so) you tell them to stop they should.
Alot of owners have trouble with this leash thing, I can tell the dog to knock it off in class, and just walk towards them in a very calm and confident manner, take the leash in hand, snap my finger for attention, tell them EH! and they look at me I have scowl on my face and I point a finger at them and they drop it, I praise them and give them a toy to chew and praise them for chewing on it..
If you get frustrated at them they try and play with you to calm you down and all kinds of puppish stuff, it is really hard to not get frustrated, it one of the hardest things to teach my students.
Good Luck,, let us know how it's going.
P.S. sorry your trainer was inadequate, there are some out there that shouldn't be doing this.
Try another if possible, watch them, see if they have control of their class, watch how they move around the room etc..every trainer is diff.