Laravel 模型关联 hasManyThrough 反向关联怎么配置

schools:
    id
    name

grades:
    id
    name
    school_id

students:
    id
    name
    grade_idCopy

public function students()
    {
        return $this->hasManyThrough(
            Student::class,
            Grade::class,
                'school_id',
                'grade_id',
                'id',
                'id'
        );
    }Copy

public fuction school()
{
  return $this->grade()->school(); 
}Copy