4 sentences

1. 同学们正在操场上做操。

   tóng​xué​men zhèng​zài cāo​chǎng shàng zuò​cāo.

   The students are doing exercises on the playground.

   Source: Dong Chinese Dictionary

2. 老师走后，同学们在教室里都很老实。

   lǎo​shī zǒu hòu, tóng​xué​men zài jiào​shì lǐ dōu hěn lǎo​shi.

   The students were very well-behaved in the classroom after the teacher left.

   Source: Dong Chinese Dictionary

3. 老师要求同学们在课上背诵德语字母表。

   lǎo​shī yāo​qiú tóng​xué​men zài kè shàng bèi​sòng Dé​yǔ zì​mǔ​biǎo.

   The teacher asked the students to recite the German alphabet in class.

   Source: Dong Chinese Dictionary

4. 他在数学竞赛中拿了一等奖，让同学们对他刮目相看。

   tā zài shù​xué jìng​sài zhōng ná le yī​děng​jiǎng, ràng tóng​xué​men duì tā guā​mù​xiāng​kàn.

   Winning first prize in the math competition made his classmates see him in a new light.

   Source: Dong Chinese Dictionary