Aggressive Dog Training in Houston?

Hi guys!! My mom rescued an “aggressive” dog from the streets and has grown very attached to the dog. He is not friendly to other dogs and does not like other people other than my mom and I. I am looking for a place to train him so he isn’t “aggressive” and can be friendly to prevent any accidents. He is very sweet and smart and we are aware of the cost and time, but it will be worth it. If you have any recommendations please let me know. We want to ensure that he’s treated right and we will see improvements in his behavior. Thank you in advance!