The comparative study explores the phenomenon of lexical cross-linguistic influence on high school students' writing performance within two distinct regions of Morocco: Rabat-Sale and Souss-Massa. Using James Taxonomy as a framework, written narratives produced by 200 students from both regions were analyzed focusing on their lexical choices and the occurrence of lexical errors. Distinct patterns of lexical errors, including Calque, Prefix, Over-inclusion, Borrowing, and Omission errors, were identified in students' narratives. The results revealed notable differences in lexical errors between the Souss-Massa and Rabat-Sale regions. Souss-Massa students exhibited higher frequencies of Calque (25), Prefix (20), Over-inclusion (35), and Omission (28), indicating a stronger influence from other linguistic sources and potential issues with precision and clarity in their writing. In contrast, Rabat-Sale students showed a higher frequency of Borrowing (28), suggesting a greater tendency to incorporate foreign language elements into their writing. These results have implications for tailored language education and curriculum development in Morocco and emphasize the importance of considering regional linguistic nuances.