At the end of twelfth grade, American students receive the high school diploma.

在念完十二年级以后，美国学生会获得高中毕业文凭。

The poll involved more than 2,000 parents of students from kindergarten to twelfth grade.

这项民意调查涉及从幼儿园到十二年级的2，000多名学生家长。

And so, what I did was, I went out and bought grammar books from first to twelfth grade. I reread them.

所以，我所做的就是，我出去买了从一年级到十二年级的语法书。我重读这些书。

Twelfth grade is the last grade of high school in an American school system.

十二年级是美国学校系统中高中的最后一个年级。

It won the top prize in a local contest run by the Air Force, even though the competitors included students through twelfth grade.

在当地一项由空军举办的赛事上，尽管参赛者中还有十二年级的学生，但这台计算器还是赢得了最高奖。

In twelfth grade, he built an electronic metronome—one of those tick-tick-tick devices that keep time in music class—and realized it sounded like a bomb.

高中四年级的时候，他做了一个电子节拍器——音乐教室里用来打拍子的、会发出“滴答”声的装置。然后他意识到“滴答”声听上去很像是炸弹定时器的声音。

You haven't been on a date since the twelfth grade, and suddenly you're booking two a day?

高三以后你就没怎么约会过了，现在你一天约两个？

Now, this is a little different from a similar term, " class president." Each level in a high school (that is, in a typical high school), a ninth grade, tenth grade, eleventh grade, and twelfth grade – those are the four levels.

现在，这与类似的术语“班长”有点不同。高中（也就是典型的高中）的每个level，九年级，十年级，十一年级，十二年级，就是四个level。