-- Removes presentation-grade synthetic reputation defaults. Existing measurements
-- are retained; unknown measurements remain NULL until backed by verified data.
ALTER TABLE `teacher_performance_metrics`
  MODIFY `avg_response_minutes` INT NULL DEFAULT NULL,
  MODIFY `response_rate_percentage` DECIMAL(5,2) NULL DEFAULT NULL,
  MODIFY `raw_avg_rating` DECIMAL(3,2) NULL DEFAULT NULL,
  MODIFY `weighted_student_rating` DECIMAL(3,2) NULL DEFAULT NULL,
  MODIFY `ai_engagement_score` DECIMAL(5,2) NULL DEFAULT NULL,
  MODIFY `sla_speed_score` DECIMAL(5,2) NULL DEFAULT NULL,
  MODIFY `mastery_impact_score` DECIMAL(5,2) NULL DEFAULT NULL,
  MODIFY `composite_merit_score` DECIMAL(5,2) NULL DEFAULT NULL,
  MODIFY `star_equivalent` DECIMAL(3,2) NULL DEFAULT NULL,
  MODIFY `reputation_tier` VARCHAR(100) NULL DEFAULT NULL;

ALTER TABLE `teacher_reviews`
  ALTER `student_watch_percentage` SET DEFAULT 0.00,
  ALTER `socratic_accuracy_rate` SET DEFAULT 0.00,
  ALTER `is_verified` SET DEFAULT 0;