Parents' immersion in smartphones has left some neglected children starting primary school unable to hold conversations, new British research warns.
Almost a third of children starting school are not ready for the classroom, with many lacking social skills, having speech problems or not toilet trained, the survey of senior primary school staff has found.
Teachers warned of children suffering from a lack of attention and interaction from parents obsessed with their smartphones.
One head teacher said: "There is limited parent/child interaction. Four year-olds know how to swipe a phone but haven't a clue about conversations".
Another primary school leader warned: "We are having more and more children entering our early years stage with delayed speech and a lack of school readiness.
"I feel much of this is down to challenging family circumstances alongside the rise of mobile phones and other mobile technology, which means parents are more often to be seen on the phone than talking to their children."
The survey of more than 1100 senior primary staff carried out by The Key, an information and advice service for head teachers, estimates at least 194,000 children could be ill-prepared to start school in September.
The State of Education report found about 80 per cent of teachers were worried about poor social skills or children having speech problems. More than two-thirds had seen children lacking "self-help skills".
Teachers also reported levels of reading, writing and numeracy were lower than they should be.
Fergal Roche, The Key chief executive, said: "School leaders are already struggling to retain staff and manage their teachers' workload, so add thousands more pupils arriving ill-prepared for the classroom to the equation, and the burden placed on our schools will be huge.
"An agreed definition of what school-readiness means could be the first step to helping schools, parents and early years practitioners identify what national or localised support is required to meet this growing issue."
Gareth Jenkins director of poverty policy at Save The Children said the report "provides yet further evidence that too many children are not getting the support they need to thrive in their early years".
He said: "Research for Save The Children has shown that falling behind in their early years can drastically limit a child's chances of success later on, affecting results throughout school, and even earnings as adults."
Last year, a leading child psychiatrist suggested parents enforce a "talk not tap" rule at the dinner table to stop smartphones and tablets taking over children's lives.
Dr Hayley Van Zwanenberg, of the Priory clinics, warned that children "transfixed" by social media and messaging risk growing up emotionally stunted and unable to cope properly with the real world.