Management is for improving outcomes from groups of people (Zhou), the better a person can achieve an outcome by orchestrating a team, the more successful they have been at managing the team.
If the outcome you care about is educating children, then a great manager’s team will better prepare students for the future than an average managers team. A bad manager’s team fails to give kids the skills and knowledge they need to thrive.
If the outcome you care about is getting amazing designs, then a great manager’s team will consistently deliver concepts that wow. A mediocre manager’s team will produce work that gets the job done, but doesn’t stand out. A bad manager’s team will regularly suggest proposals that make you think, /Surly we can do better than this./ Julie Zhou, The Making of a Manager