需求：
列出全校全部学生名单，要求将同一个班级的学生分散排序。即首先从各个班级中抽取1个学生，直到全部班级的学生都抽完。每个班的学生数不同。还需要实现分页。
示例数据：
表school:
id      class_id    student_id       student_name
1        1                1                        s
2        1                2                        a
3        1                3                        b
4        1                4                        u
5        2                1                        e
6        2                2                         t
7        3                1                        o
8        4                1                        p
排序后的结果：
id      class_id    student_id       student_name
1        1                1                        s
5        2                1                        e
7        3                1                        o
8        4                1                        p
2        1                2                        a
6        2                2                         t
3        1                3                        b
4        1                4                        u
说明：先从班级1234各抽出1个学生，然后从班级12中各抽出1个学生，然后从班级1中抽出最后2个学生。