Assessments play a pivotal role in Mathematics education, serving as vital gauges of students' mathematical proficiency and informing teaching strategies. Despite calls for contextualization, some educators still rely on abstract teaching methods and decontextualized tasks. This study aims to address these concerns by designing and implementing a performance task on quadratic functions, following a realistic mathematics education approach, coupled with metacognitive prompts. Using mixed methods, pre-test and post-test scores from the Jr. MAI of 30 Grade 9 students, their responses to metacognitive prompts, performance task scores, and interview questionnaire responses were analyzed. Statistical analysis revealed significant improvements in students' metacognitive awareness and skills, particularly in knowledge about cognition and regulation of cognition. Strong positive correlations were observed between variables. Descriptive analysis indicated an increase in students scoring above the cut-off post-intervention. Thematic analysis of student interviews highlighted themes such as pre-task planning, progress monitoring, and post-task evaluation, underscoring enhancements in self-knowledge and mathematical performance.