This descriptive research study aimed to assess the management of the existing policies, guidelines, and procedures on the implementation of the interdisciplinary approach in performance-based assessment (IAPA) before and during Coronavirus disease (COVID-19) as a basis for proposing improvements for its implementation in the "new normal". 30 senior high school science teachers and school leaders from 5 private and 5 public schools in Metro Manila, Philippines, participated in this study. The participants assessed the management of existing policies, guidelines, and procedures on the IAPA's implementation using a survey questionnaire and identified its strengths and weaknesses using an interview guide. The researchers developed the instruments used for data collection but subjected to experts' validation and reliability test. Results reveal that the management of IAPA was effective and that it benefits students and teachers in many ways. However, it has also weaknesses, which are associated with the role of school leaders in the implementation of the policies, guidelines, and/or procedures, especially during the new normal education setting. The study provides suggestions for improving IAPA implementation in the new normal covering both the face-to-face and online learning modalities.