I have a 6 year old boxer/pit...

Question
I have a 6 year old boxer/pit bull cross (?). We got him from the
SPCA, one year ago. He is submissive to family members, but is
not so with all dogs. He gets excited and barks at the ones he is
not comfortable with. At which point, I'm yanking on the leash
and talking to him with no effect. He is off leash every morning
and will come back to me unless he is involved with another
dog. How do I get him to calm down a little and listen to me  
when other dogs are around? Is it better to leash him when he
gets to excited, or let him work it out with another dog?
Thanks in advance.

Answer
Once a dog is 6 years old, it is hard to change its personality.  This is even more so if you are fighting an inborn trail.  Pit Bulls were bred to friendly to people, but aggressive to other dogs.  People tend to panic at the mention of Pit Bulls.  He will be held to a stricter standard than for other breeds, however unfair.  

The next question is whether it is true aggression or rough play.  Wrinkled noses, hackles up, and low growls mean trouble.  It the other dog runs off as soon as it gets a chance, that is bad too.  Society will not tolerate an aggressive dog running loose.  If he really is aggressive, you must keep him on leash whenever you may encounter other dogs.  Most other dogs would quickly submit to him without a fight.  Some smaller dogs might defy him and end up injured.  Then you would have a mess.  it is also possible he could attack a larger dog and get the worst of it.  

If you are yanking on a conventional slip collar and not getting results, try a head collar.  The leading brands are Promise,  Haltie, and Gentle Leader.  They have a strap going around the dogs nose looking something like a muzzle.  They work
by pulling the dogs head around.  No other way gives you such great control
with so little force.  The prong collar is now a dangerous relic of value only
for its macho looks.  Do not consider using one without hands on instruction
from somebody with plenty of experience with them.