Schools are removing analogue clocks from exam halls because teenagers are unable to tell the time.
A head teachers' union has said that digital devices are replacing circular clockfaces after pupils sitting their GCSEs and A-levels complained they were struggling to read the right time.
Malcolm Trobe, deputy general secretary at the Association of School and College Leaders, said pupils had become accustomed to digital display.
"The current generation aren't as good at reading the traditional clock face," he said.
"They are used to seeing a digital representation of time on their phone, or on their computer."