It is always important to discuss neutering with your vet, or even seek the advice from a couple of different vets. Accepted medical guidelines say dogs can be neutered after 6 months old. For female dogs, some wait until they have had their first season before being spayed. For male dogs, particularly bigger breeds, some wait longer until the dog has reached sexual maturity before castrating.
By the time unneutered male dogs reach sexual maturity at around 12 months, they begin to be governed by their hormones. The social issues of an unneutered male can be especially pronounced in a doggy day care setting, because there are a number of dogs together for extended periods of time.