This article analyzes the results of a study on the situation concerning the educational achievements of girls and boys in the STEM field in Latvia. The study was conducted at the compulsory education level to understand the conditions in the learning environment that can predictably affect the academic achievements of girls. For the purposes of the study, a survey questionnaire was developed, which was filled out by 1847 students from the 7th–12th grades. The obtained results show which factors affect learning achievement in STEM subjects for students with low and high learning achievements in groups divided into boys and girls and which pedagogical activities can predictably improve STEM learning achievements. The research data confirm that there are differences in predicted learning achievements in groups of boys and girls with high learning achievements, depending on the pedagogical strategy used. Additionally, the results of the study confirm that the most significant factor for a predictable increase in learning achievements in the STEM field is students liking mathematics and, in the case of high learning achievements, them liking chemistry. An indicator that has a significant negative impact on academic achievement in STEM subjects is a dislike of physics, which appeared in the group of girls with low academic achievements. Liking other STEM subjects to improve student achievement did not appear statistically significant in any of the analyzed groups. This study is essential to supplement the knowledge base on gender differences in learning achievements in STEM subjects and is also important for the educational space of Latvia because the learning achievements of girls in the STEM field are lower in this country than it is for boys. The obtained results show which methods of pedagogical work have a higher impact on increasing the predicted learning achievements and also show potential future research directions.