female spaying and aggresiveness

Question
We have a pure bred female golden retriever that we wanted to breed so did not get her spayed. She goes to "doggie day care" but just today we were told that she can't come back because she was aggressive towards one of the smaller dogs. If we spay her, and forgo the breeding, will that make her less aggressive? She has gone thru two heat cycles, and is approaching her third in a month. We would not be able to breed her until she gets a hip check etc. but I am very unhappy for her not being able to go to day care while I am at work. If spaying her will make her less aggressive, then we will do it, but so far, I've only read that neutered males are less aggressive.

Answer
Spaying should also reduce aggression in females just a neutering does in males.  It also is highly effective in preventing passing on aggression and other temperamental problems.  If this aggression is new, it could be part of the flaky behavior that is the first sign of a female's approaching heat cycle.  

The dog world has far more need for homes for dogs than more people breeding.  Just how well have you thought through why you are thinking of breeding her?  Is she an outstanding dog with many fine traits to pass on?  Note, my standards on that questions call for more than success in the show ring.  The most rational thing for most pet owners is to spay/neuter and forget breeding.  There is an excellent discussion on breeding at http://www.woodhavenlabs.com/articles.html#breeding  It is true that as a breeder, the owner of the site would be a little biased against competition.  I love his balanced approach to some other things such as chow.  Any info needs to be evaluated for its source's interests.