leash aggression

Question
my 5 year old shepherd/terrier cross is the most well-mannered dog-- except when he's on a leash! we have followed all dog training advice, and cannot rid him of the aggression. he does not bite other dogs, but he lunges at them, barks, and sometimes causes fights.

for the first two years, we tried to correct his behaviour by putting him into a sit, and then down. praising and rewarding him for quiet and good behaviour.  this did not work. his behaviour escalated!

the last bit, we've been reprimanding him by actually bringing him down to the ground. he's a big dog, so this is quite a hassle. he gets a very firm NO! and then yanked down by his choke to the ground. this has had better results than the former, but is not practical and bothers me to do. i don't like that he freaks out everytime he sees another dog, and because of his size, he can be quite scary. the direct punishment has helped enough so that he occasionally control himself.

the crazy thing is that he is never like that off leash, and actually is a very well-trained dog. he heels to my heel, listens well normally, plays with many other dogs (off leash, obviously). he is well socialized and exercised.

is this something i am just going to have to live with? i wish that i could figure out how to correct the behaviour!!!!!! i feel that i am seeing some results from putting him down on the floor by his choke (i don't hurt him, but it's firm) but i am afraid that this will just further his issue with leashes.

btw, it's just strange dogs... the neighbours dogs are fine when he's on leash.

help!

taai  

Answer
Good Day taai,
 I am so sorry to hear of your problem.  Sounds like you are trying to do everything right.
 I can go on and on with legnthy emails that you still wouldn't get about this subject.  My suggestion is to get a professional trainer to your house to work on this one on one.  It can still be helped.

Sorry I couldn't be of assistance.

Sincerely,
Tammy