Teachers who want detailed scientific analysis of whether their students are paying attention to their lessons may soon have a new weapon at their disposal: biometric bracelets.

The bracelets, which indicate engagement and “emotional arousal” by monitoring sweat levels, are due to be trialled in schools from April in a controversial study funded by the Bill and Melinda Gates Foundation. Shaundra Daily, the researcher behind the experiment, hopes that the so- called “galvanic skin response” devices will empower teachers by measuring reactions to their classes.

“Some teachers are very, very good at just looking at their students and gathering cues in that way as to how they are receiving the lesson,” the assistant professor at Clemson University, South Carolina, told TES. “But some teachers could use some extra support.

“This could empower them to better understand how students are receiving what they are doing in the classroom. They could then tweak things in the lesson that they wouldn’t have (otherwise) known to pay attention to.”

The project sparked debate when plans for the experiment first came to light in 2012. Educationalists were particularly concerned that the devices, sometimes dubbed “mood bracelets”, could be used to evaluate teacher performance.

Diane Ravitch, assistant education secretary under former US president George HW Bush, claimed that the idea was “madness” and “crosses the line from legitimate research to investing in technologies to control and manipulate people by monitoring their emotions”.

The Washington Post education blogger Valerie Strauss described the scheme as “a bit creepy”, writing that “the obsession with measurement in data and school reform has reached nutty new heights”.

But Dr Daily stressed that her research was aimed at helping teachers, not finding ways to judge them. The Clemson team has used the $500,000 grant from the Gates foundation to develop a video and graphics package to be used by teachers to help interpret and provide context to the data gathered from the bracelets. It includes video footage of a lesson accompanied by computer generated circles that turn green or red depending on the level of individual students’ emotional stimulation.

Dr Daily hopes that the technology can eventually be developed to provide teachers with live information about their students’ emotional reactions to lessons.

“We hope that there would be a tool to measure engagement and provide teachers and students something they can look to for real-time, or reflective, feedback - kind of like a pedometer,” said Dr Daily, an electrical engineer who specialises in education technology. “A walking pedometer unobtrusively measures steps.An engagement pedometer, we hope, will measure engagement.”

The system is now almost ready for trials, which will be conducted with teachers of 10- to 12-year-olds in two or three schools (unnamed because of research regulations) in the south-east of the US. The results are expected in June.

Dr Daily accepts that there are limits to what the bracelets can identify. For example, they will not be able to distinguish between engagement and anxiety, or relaxation and boredom. Dr Daily also acknowledged that increases in student stimulation picked up by the sensors might not necessarily be caused by the teacher. “It could be that the bell rang or that someone sneaked up behind you,” she said.

Many teachers have written to Dr Daily to express fears over privacy, which she has taken on board, she said. Dr Daily added that the technology would be best suited to use in teacher training programmes, but acknowledged that school leaders could use it to judge teachers.

“Of course people might want to try to use it [for teacher evaluation],” the academic said. “Golf clubs were not created to hit people with but people have been hit by golf clubs. But this tool is more powerful and has more of a chance of making an impact if it is used in the way it was intended.”

Don’t sweat it

Galvanic skin response bracelets exploit a relationship between the nervous system and emotional stimulation, sharing an approach used by lie detectors.

When external or internal stimuli that are physiologically arousing occur, sympathetic nervous activity increases. The skin, in turn, momentarily becomes a better conductor of electricity. Or, to put in it plainer terms, it sweats.

This level of sweat can be measured using sensors in the bracelets that can also pick up temperature and motion.