First of all congrats for planning your major in Junior year! Beyond the degree, the kind of work you are looking into requires patience, empathy and people skills. If you are planning on developing these personal skills, you are going to enjoy this field. In order to work as a mental health professional or a social worker you would need a bachelor's / master's degree in the related field. Majoring in Psychology or Social Work should be fine. It's difficult to find a decent paying job if you just have a bachelor's degree. Most jobs in these fields look for advanced degrees and training. If you major in Psych you can do your master's in Counseling Psych or School Psychology too. The scope is border when you do your master's.