Yes, 12th-grade marks can matter when applying to study abroad for an MS to some extent. While universities primarily focus on undergraduate and standardized test scores (like GRE or GMAT), a strong overall academic record, including high school grades, can bolster your application. Additionally, a good 12th-grade performance might be necessary for scholarship eligibility or if the program has specific prerequisites. However, other factors like letters of recommendation, statement of purpose, and relevant experience often carry more weight in the admissions process. It's essential to check individual program requirements and prioritize them accordingly.