Kathy- I am searching down some folks in the hope that they can help. I promise to get back to you on this. Thanks for posting on The Mandarin Center!

Hi Kathy,

Here are my thoughts -
1. Are any of these 成語 obsolete or rarely used?
Out of the ones listed, these are more commonly used -

一路平安
一見如故
一心一意
一言為定
人山人海
刀山火海
三心二意
開門見山
天下太平
火上加油
膽大包天

2. Do any of them have other interpretations that are inappropriate for a high school setting?
No.

3. Do you have any favorite 成語 that use 3-4 very simple characters?
I would try the ones you listed and see how it goes. I was teaching numbers to my Mandarin 1 beginners (high school) and I introduced a few simple 成語 such as 一石二鸟 to my heritage students but even they seemed to be lost. I believe it's important that you teach 成語 in context that's relevant to your students.

I hope this helps.

Hi Kathy,
Thanks for posting your question!

Megan and Liulaoshi,

Thanks so much for replying to my question--I really appreciate the feedback and will let you know how things go with this.

I totally agree with the need to introduce chengyu in ways that are useful and relevant.

All the best,

Kathy

Hi liulaoshi,
Thanks for posting your answer!

I am Lily! We all know that Each Chinese idiom, or Chengyu, is a short phrase, usually with a Chinese story with significant and interesting meaning, and accompanied with Pinyin and English annotation. Chinese idioms usually consist of four characters. A Chinese idiom story will not only tell you the meaning of a phrase, but also help you learn more about ancient Chinese culture.

Example: 调虎离山(Diàohŭlíshān)
To lure the tiger out of the mountains

Idiom Story
At the end of the Eastern Han Dynasty, warlords possessed many parts of the land. Sun Ce was only 17 years old, but young and promising. He followed in his father's footsteps and his power began to grow. In AD 199, Sun Ce wanted to advance further and managed to occupy Lu Jiang county in Jiangbei. Liu Xun was the ambitious and powerful warlord of Lu Jiang county and so in order to neutralize him Sun Ce organized a Coup. Sun Ce knew that Liu Xun was extremely greedy and so sent him a precious gift with a letter praising his achievements and asking for him to kindly surrender Jiangxi. After receiving the gift and reading the letter Liu Xun decided to banish Sun Ce from his kingdom once and for all and ordered his army to attack. On seeing the soldiers readying for attack Sun Ce reportedly said "The tiger has come out, and we will now occupy Lu Jiang." And Lo and behold they did. Now this phrase is used to mean luring or manipulating others into a position of weakness which can then be exploited. .

Example
他使用调虎离山之计打赢了这场战争。
Tā shĭyòng diàohŭlíshān zhī jì dă yíng le zhè chăng zhànzhēng.
He used the way of luring the tiger out of the mountains to win the war.

Article Resource: http://www.echineselearning.com/free-trial/index.html?ecl=ptEEEEEEtmll01...