In recent years, the need to level out students’ knowledge before they join a university degree has become evident. Many institutions offer leveling courses for first year students, mainly related to basic subjects such as mathematics or physics in the case of science degrees. This need has also been detected in more advanced subjects offered as elective. Several factors condition this situation. The fact that a subject is elective implies that even students following a formative path with low affinity can select the subject. Moreover, this type of subjects are often chosen by interchange students to complete their curricula. In this work, the case of an elective subject in the Agricultural Engineering program in Universitat Politècnica de València is analyzed. The subject “Vegetable Plant Breeding” was offered in the fourth academic year and English was the medium of instruction. As a consequence, there was a high rate of registration of interchange students coming from different universities and from different programs. The number of students in the four academic years analyzed ranged between 17 and 45. A survey of previous knowledge was carried out in two of the academic years. The survey included 28 items related to three different areas: practical experience in nine different techniques, management of specific terminology for 12 concepts, and theoretical knowledge of seven different topics, in all cases related to the subject. For the two first areas (practical experience and terminology) students were asked to answer if they have or not previous knowledge, while the theoretical knowledge was ranged between 0 (none) and 3 (high). These surveys evidenced that even the students that followed affine subjects in previous years perceived that they lacked key concepts necessary to understand plant breeding. Moreover, a leveling test was conducted at the beginning of the course for four academic years, related to molecular genetics, one of the previous knowledge necessary to better follow the course. Significant correlation was found between the result of the leveling tests and performance in the subject. Different strategies were used to level out students’ knowledge. First, students were provided with teaching materials in different formats (written documents, videos, internet resources, …) related to the recommended previous knowledge. Secondly, a review class was taught, specifically devoted to molecular genetics. The leveling test was repeated after this review class and marks obtained were significantly higher. The highest grades for the course were obtained by either the students coming from affine programs or those who used the teaching materials designed to level out their knowledge.