The aim of the study was to evaluate the possible differences in linguistic skills and school achievement between girls and boys. In a nation-wide study, the achievement of 1,936 second-grade Finnish girls and boys was appraised according to the teachers’ rating. The results were compared with the linguistic test performance of 364 pupils from the nearby area. The mean rates of girls in writing, reading, oral performance and attention were significantly higher than those of boys as evaluated by the teachers (p < 0.01). Also, the risk of boys to be below the median in their achievement rates compared with girls was higher (risk ratios 1.3–1.6, 95% confidence intervals 1.2–1.7, p < 0.01). In multiple regression analysis where birth order, duration of nursery day care, number of otitis media episodes and parental education were controlled for, male gender proved to be a risk factor for linguistic skills as graded by the teachers. Yet, performance in linguistic tests did not support the superiority of girls in linguistic skills. Professionals taking care of linguistic problems in children should be aware that teachers’ evaluations are influenced by the gender of the pupil.