many children are not ready to sit down and do reading , writing and maths when they start school at the age of four or five , according to the national union of teachers -lrb- nut -rrb- .
at its annual conference in harrogate , it will say schools should follow the lead of countries like finland and introduce 45-minute lessons immediately followed by 15-minute play times .
teachers want children to have more play time to encourage greater communication and social skills .