Advice please

My 6 year old springer is driving me mad, at home he is sweet and timid very quiet, take him out and he turns into a monster. He yelps and screeches, pulls on his lead and is generally hyper, he has also started to be aggresive towards smaller dogs
We take him to obedience classes weekly and he is vocal but ok and loves it, we also take him to agility and again he loves it and does really well but again this is spoilt with his yelping and flying towards the smaller dogs for no reason.

I just dont know what to do with him, I feel like keeping him behind locked doors all the time but I cant do this, we also have 4 other springers who are fine.

Springers are bred to be very active and if he is well behaved at home you are fortunate, my guess would be that when he does go out he just explodes with pent up exuberance. Are you able to increase his activity level particularly activity where he has to use his brain. Think that is what is needed more to do so he can uses his natural desire to work.

Hi this link may be intresting to you, it sort of describes the poss situation you could end up finding yourself in,

http://www.dogsey.com/showthread.php?t=83641

my advice is up his outdoor exercise, up his mental stimulation,, over the next week try doing twice as much as you do now,, it may help to bring him back to a more normal level to work with, best of luck,

hey- was just wondering if your dog is fairly new to your family or if this is an old/new problem. Asking as you say that he is 6?

No we have had him from 13 weeks, he was never like this, it has started up in the past 6 months, before that he was fine with any dog. He has just taken an instant dislike to small dogs and I dont know why, he is fine with big ones.