Writing is a complex activity. If a child’s preparation for writing, which begins to develop in the preschool years, is poor, this can inhibit writing and cause problems. Because children are expected to know how to hold a pencil correctly, how to sit correctly while writing, and how to prepare and adjust the writing surface without planning, this study seeks to determine how first graders are prepared for writing in terms of selected biomechanical and ergonomic factors at the beginning of the school year. The goal was to determine whether there are any differences between students according to sex and handedness and if there is any connection between basic pre-writing skills and the ergonomic suitability of furniture (table and chair size). An empirical study was conducted involving 246 first graders from randomly selected public primary schools in Ljubljana, Slovenia, and fifteen of their female teachers. The results of the research showed that inadequate furniture size affects how students sit and that there are statistically significant differences between the positions of the writing surface for right-handers and left-handers. The research did not show a correlation between posture and pencil grip, but it is very likely that it would have been demonstrated in a larger sample. No sex differences were found between pencil grip, writing surface position, and posture; no connection between handedness, pencil grip, and posture; no connection between pencil grip, poor posture, and writing surface position; and no connection between posture and ergonomically appropriate school desks and chairs.