Greater expectations can lead to better performance and better results, while the lower expectation can lead to a low performance.
The "Pygmalion effect" or "Rosenthal effect" refers to the phenomenon that higher expectations can increase performance. Professor Robert Rosenthal was the first to demonstrate it. In a California elementary school, he conducted an experiment and discovered that when teachers are made aware of students who have a high chance of success, their expectations rise. As a result, they paid special attention to those students and sometimes treated them differently. Essentially, the teachers subconsciously acted differently toward those students, which promotes their success. This has a positive impact on the student, and their performance improves as a result.