3 sentences

1. 他因为严重违纪被学校开除了。

   tā yīn​wèi yán​zhòng wéi​jì bèi xué​xiào kāi​chú le.

   He was expelled from school for a serious breach of discipline.

   Source: Dong Chinese Dictionary

2. 他因为严重违纪被学校勒令退学。

   tā yīn​wèi yán​zhòng wéi​jì bèi xué​xiào lè​lìng tuì​xué.

   He was expelled from school for serious disciplinary violations.

   Source: Dong Chinese Dictionary

3. 我们将准此原则对违纪行为进行处理。

   wǒ​men jiāng zhǔn cǐ yuán​zé duì wéi​jì xíng​wéi jìn​xíng chǔ​lǐ.

   We will handle disciplinary violations in accordance with this principle.

   Source: Dong Chinese Dictionary