编写sql语句，计算每个学校、每个年级、每个班的各科平均分、最高分、及格人数，其中及格分数线为90分

编写这样的SQL语句涉及到多级聚合和条件判断，假设我们有`grades`表，包含以下字段：`school_id`, `class_id`, `grade`, `subject`, `score`。下面是一个示例结构的SQL查询：

WITH scores_per_class AS (
  SELECT
    school_id,
    class_id,
    grade,
    subject,
    AVG(score) OVER (PARTITION BY school_id, class_id, grade, subject) as avg_score,
    MAX(score) OVER (PARTITION BY school_id, class_id, grade, subject) as max_score,
    COUNT(CASE WHEN score >= 90 THEN 1 END) OVER (PARTITION BY school_id, class_id, grade) as passing_students
  FROM grades
)
SELECT
  s.school_id,
  s.class_id,
  s.grade,
  s.subject,
  s.avg_score,
  s.max_score,
  s.passing_students
FROM scores_per_class s;

这个查询首先通过窗口函数（Window Function）计算了每个班级、学科的每个年级的平均分（avg_score）、最高分（max_score），以及及格的学生人数（passing_students）。这里的CASE WHEN语句用于检查分数是否大于等于90，并统计符合条件的数量。