Final answer:
The middle stage of moral development is the conventional level, where strict adherence to societal rules and the approval of others determine what is moral.
Step-by-step explanation:
The middle stage of moral development, according to Lawrence Kohlberg's theory, is the conventional level. This level is characterized by strict adherence to societal rules and the approval of others influencing one's sense of morality. At this stage, individuals consider what society considers moral and immoral as their guide for determining right and wrong behavior. Therefore, the statement is true.