First, can I correct the grammar of your statement? It should be 'performance', not performances. In the sense of success or achievement of results, 'performance' is uncountable, so it cannot be in the plural form. Only actors, musicians and dancers have 'performances'. Performance, in a professional context, is a quantifiable measure of what a person achieves. For example, a teacher's performance can be measured according to their students' exam results. A doctor's performance can be measured according to how well their patients recover from their illnesses. The question is asking whether or not you think doctors and teachers should be 'graded' according to the results they achieve. So do you think that a teacher whose students all pass their exams should graded higher than a teacher whose students don't do so well? Do you think their should be A,B and C grade teachers, and maybe the A grade teachers should be paid more? What about doctors? Should we count up how many of a doctor's patients get better, how many stay ill, and how many die? And can we say that the doctor who has more patients recovering from their illnesses is a 'better' doctor than one who has fewer patients getting better? Is this a fair system or not?

It means, "An evaluation of the quality of a doctor or teacher should be based on the results they achieve." It implies judging them this way rather than on other factors,such as experience and education. Does that help give you some ideas? What are these ideas?