This pilot study explores the impact of linguistically informed formative assessments on English as a Foreign Language (EFL) proficiency among Greek learners, focusing on primary and secondary education establishments. Leveraging five years of research data collected between 2017 and 2022 from over 360 students across urban and rural regions in Greece, this study examines how integrating linguistic theory into formative assessments can enhance students' morphological and syntactical proficiency. Using a mixed-methods approach, both quantitative and qualitative data were gathered through standardized language proficiency tests, linguistically informed assessments, and semi-structured interviews with students and educators. The findings indicate that students exposed to these linguistically informed assessments demonstrate significant improvements in EFL proficiency, particularly in verb conjugation and sentence structure, with enhanced long-term retention and application in both written and spoken English. These results underscore the potential for linguistically informed formative assessments to be a powerful tool in EFL pedagogy, with implications for curriculum design and instructional practices in Greek educational settings. The study also identifies areas for future research, including broader applications across diverse educational contexts and the scalability of such assessments.<p> </p><p><strong> Article visualizations:</strong></p><p><img src="/-counters-/soc/0760/a.php" alt="Hit counter" /></p>