Standard Poodle - aggressive towards young dogs

Question
I have a 11 month old black standard poodle who is showing aggression towards dogs who are his age or younger. It seems to not matter if they are male or female. He has not been neutered yet on advice of breeder that recommended I wait until he was mature ( year and a half ).  He is very well behaved otherwise and follows all basic commands and comes when I call him. He is very protective and will barck quite intensly when someone comes to the door or walks past the house but he quiets quickly when I command him to. I have a 4 yr old son and older teen children all of which he is well behaved and gentle with. He does not listen as well with them and it seems he regards me as pack leader. I am very stressed about this behaviour and it has impacted where we walk and when. I have had to isolate him because if we pass 20 dogs he will be fine , playful or indifferent but if we encounter a dog who is a year old or younger - all hell breaks loose ..

I plan to neuter his asap but I am concerned this behaviour will be established and / or imprinted

thank you for your time

Answer
Hello Barbara,
Getting your dog neutered now is a good idea as the older he gets the more testostrone he will produce.  This increased hormorne can lead to a dog thinking its dominate, which can also lead to increased aggression.  

You need to start dominating your dog to let him know that you are his boss and he needs to submit to you.  At home this means laying him down on his side and holding him down until he submits to you, then walking away and letting him up.  When you are out on walks, you need to keep him from focusing on the oncoming dog, and onto something else.  Make him sit or down, and turn him away from the other dog so that he can't stare the other dog down.  
If you need to, put him in the submissive position right there on the sidewalk.  Make him submit to you until the other dog walks by.  

Give this a try and see how he reacts.  You may need to keep at it for awhile, but eventually he will calm down for you.  

If you have any other questions for me, please feel free to ask and sorry it took so long to get back to you.

Thanks for using AllExperts.com,
Kim