Expulsion can be seen as a disciplinary tool. Many schools make use of this and it involves not allowing a particular student to attend school. Depending on the severity of the act committed, the time period for which the student cannot attend school can be short or long. Most of the time expulsion tends to be permanent and the student is not allowed back and this is something which goes in his/her permanent record.
A student is generally not expelled for petty reasons. A student is usually expelled for having violated a strict law or code of the school. Many schools in various cities have their own code of conduct which every student must abide by. If he/she fails to do so, the result generally tends to be expulsion. These policies are generally told to the student so that he/she is aware of what acceptable behavior is and what is not. This also gives them an idea of what is expected of them at school.
Some of the basic things which could result in expulsion include