Teachers and administrators face many challenges in motivating students to perform better in school. Often educators adopt rewards programs intended to recognize superlative efforts by students. Those programs may have an unintended consequence - branding or labeling students.

A dunce cap is a pointed hat placed on the heads of slow or lazy students at schools. Modern societies frown upon the use of dunce caps, but a recent case of a primary school in Xi'an has come to light in which students performing well in school were given red scarves to wear while students whose performance was judged inferior were made to wear green scarves.

In a related scenario earlier this month, students at two California high schools were provided with color-coded IDs based upon how well they had performed on standardized tests. The top performers were accorded black IDs which gave them special privileges (i.e. shorter lunch lines) and discounts at school events. The white ID cards were the dunce cap proxies.

After the scarves and ID card schemes were reported in the press, the offending schools discontinued the programs.

Psychologists have discouraged the use of color-coded labels for years. In the 1950s, my primary school tracked students into color-coded reading groups, a practice the school has thankfully discontinued. In one well-known study from 1968, a third-grade teacher in Riceville, Iowa, demonstrated that labeling students according to eye color could lead to stereotyping and prejudice.

Teacher Jane Elliot designated blue-eyed children in her class as superior to brown-eyed children. Elliott provided blue fabric collars and asked the blue-eyed students to wrap them around the necks of their brown-eyed peers as a method of easily identifying the inferior group. She gave the blue-eyed children extra privileges, such as second helpings at lunch, access to the new jungle gym, and five extra minutes at recess. The blue-eyed children sat in the front of the classroom, and the brown-eyed children were sent to sit the back rows. The blue-eyed children were encouraged to play only with other blue-eyes and to ignore those with brown eyes.

Those who were deemed "superior" became arrogant, bossy and otherwise unpleasant to their "inferior" classmates. Their grades also improved, doing mathematical and reading tasks better than before. The "inferior" classmates also transformed - into timid and subservient children, including those who had previously been dominant in the class. The brown-eyed children's academic performance suffered. In another famous classroom experiment from the 1960s, teachers in a South San Francisco classroom were told to expect that certain of their students would intellectually bloom the following year, based on the results of a test. Although the "bloomers" had been selected at random, that group showed improvement in IQ scores which the researchers attributed to the teachers unwittingly creating the behaviors they expected.

The expectations that teachers form of their students, in addition to being the result of labels given to the students, are also great determinants as to future labels. The self-fulfilling prophecy is a psychological construct in which expectations of students become reality simply because that is what is expected. The takeaway message is that our expectations can influence later outcomes.

Even were we not stigmatizing certain groups of children by rewarding others, we should carefully consider how best to provide those rewards.

In a series of 1970s experiments, Stanford psychologist Mark Lepper and colleagues found that young children who received one-time rewards for doing an activity that they already enjoyed (drawing), subsequently drew less than a matched group of children who did not receive rewards. Lepper concluded that children who associate a reward with an activity are less intrinsically motivated to perform that activity.

There is a debate fueling education in the US over whether providing cash bonuses can coax improved performance from teachers and students and whether paying students for schoolwork diminishes their ability to feel intrinsic pleasure in achievement for its own sake. Preliminary results reported this month by The New York Times suggest that under some circumstances, rewarding teachers and students monetarily for doing well on Advanced Placement exams might encourage students to work harder.

We have a long way to go before we really understand how to get all children to do their best in school. What we know for sure is that any motivational plans we devise should avoid inadvertently institutionalizing a dunce cap mentality among some of our students.

The author teaches American law courses in China through a masters program jointly sponsored by Tsinghua University and Temple University, and is a fellow at the US-based Institute for Analytic Journalism.