Secondary school students should be allowed to use Internet language (slang words) in their writing

Firstly, the idea that slang words should be used is totally not possible. Slang words have no solid definitions, compared with other words. People have different interpretations on the same slang, so some people may think that the student used it wrongly while some may think it is correct. 

Secondly, students should learn the formal way of writing. Slang is part of our lives, so do formal words. School is a place for students to prepare for the future, especially in the work force. Formal language, without any slang, should be used in formal documents and many things related to their job in the future. If students are allowed to use slang in their writing, they won't have chance to practice formal writing. It will be a big problem when they go to work. Students do need to know slang, in order to communicate with friends and people around them, but they get enough practice of using slang in their daily life already.