Primary lined writing paper
Primary ruled and primary lined writing paper are the same thing, and the size you want depends on how well the child already controls a pencil.
The 1 inch rule for kindergarten
Primary paper is conventionally a 1 inch rule with the midline halfway, and that is what the default option prints. It gives 8 lines on Letter and 9 on A4, sized so a kindergarten hand fits a letter between the guides without cramping.
Extra large for preschool
The extra large option is a taller 1.375 inch rule, 6 lines to a Letter page. Choose it for preschool or for a child whose letters still run over the lines, because a bigger band forgives less precise motor control.
Moving up to wide ruled
Once letter height holds without the dots, children move to ordinary wide ruled paper at 8.7mm. That ruling and the college and narrow rulings are on the printable lined paper page.
