In a classic 1964 experiment, Dr. Robert Rosenthal randomly labeled some students in a San Francisco public school as "Bloomers", telling their teachers these kids had the special ability to make dramatic academic improvements over the course of the year.
Indeed, the randomly labeled Bloomers showed astounding improvements on standardized tests, compared to their same age peers - as a result of the higher expectations of their teachers.
More than 50 years later, a plethora of studies have shown the powerful effects of high expectations across multiple settings. As reported in a Discover Magazine article on the subject:
"... when managers have high hopes for their employees, the workers become more productive. When military instructors believe trainees have superior skills, the trainees perform better."
Even couples on the dating sight OKCupid who were told they were a good match (even though they were NOT) spent more time engaging with each other online.
Dr. Carol Dweck's lifetime of research about the Growth Mindset shows the same results. Watch her video about the Power of Yet - about ways that different expectations can lead to improved student learning, effort, and progress - especially with struggling students.