It's the way you would learn a martial art. 好比学习武术。

In a martial art, you would practice the white belt skills as long as necessary, 在武术当中，你往往必须一直练习白带(最低等级)的技巧，

and only when you've mastered it you would move on to become a yellow belt. 只有当你掌握了它们，你才能进阶到黄带。

It's the way you learn a musical instrument: you practice the basic piece over and over again, 这也是你们学习乐器的方式：一遍遍练习最基本的曲目，

and only when you've mastered it, you go on to the more advanced one. 只有掌握了它们，才能去挑战更难的那些。

But what we point out -- this is not the way a traditional academic model is structured, 但我们要清楚：这并非传统学习模式的构成方法，

the type of academic model that most of us grew up in. 并不是我们成长过程中所经历的那种。

In a traditional academic model, we group students together, usually by age, 在一个传统学习模式当中，我们一般会按年龄将学生分组，

and around middle school, by age and perceived ability, and we shepherd them all together at the same pace. 在中学时期，则是通过年龄和外显的学习能力分组，然后我们以相同的节奏引领他们。

And what typically happens, let's say we're in a middle school pre-algebra class, 最常见的情况是，假设我们身处某中学的代数预备课堂，

and the current unit is on exponents, the teacher will give a lecture on exponents, then we'll go home, do some homework. 现在的专题是指数函数，老师就此内容来上课，然后我们回家，做一些相关习题。

The next morning, we'll review the homework, then another lecture, homework, lecture, homework. 第二天早上，我们会检查这些作业。之后又是上课，做作业，上课，做作业。

That will continue for about two or three weeks, and then we get a test. 这大概会持续两到三周，就该测验了。

On that test, maybe I get a 75 percent, maybe you get a 90 percent, maybe you get a 95 percent. 在考试中，我也许只会75%的题目，你也许会90%，他可能会95%。

And even though the test identified gaps in our knowledge, I didn't know 25 percent of the material. 即使考试能帮助我们查缺补漏，还是会有25%的内容我没有掌握。

Even the A student, what was the five percent they didn't know? 就算那些得A的学生，依旧有5%的内容没搞懂。

Even though we've identified the gaps, the whole class will then move on to the next subject, 即使我们认识到那些漏洞，课堂还是会继续，进入下一个专题，

probably a more advanced subject that's going to build on those gaps. It might be logarithms or negative exponents. 可能是更加复杂的内容，但却会建立在我们的知识漏洞之上。可能会是对数函数，或者是负指数函数。