好吧，要将一个类的对象链接到同一个类（a）的父对象，只需在属性中设置它： students 表架构

id
parent_id // <--- this is the key.
name
...

/**

* this addional (and optional) attribute can help you to identify
* if this is the parent of the branch, because with
* this approach you can have grandchilds and so on..
**/

is_root // <---

然后在您的模型中：
用户.php

public function parent()
{
    return $this->belongsTo(User::class, 'parent_id');
}

现在，关于用户类型，您还可以设置一个属性来了解用户类型：

id
parent_id
name
type // <-- this could show the user type: 'student', 'teacher', etc