We should have extended school days because it will create more time to learn an extended amount of concepts and facts based on the subjects we are taught. If school is ever extended, there may be no more need for homework for students would be able to complete all work during the school day. (Note: There are mainly pros on this topic.)
This is very simple and broad, but I hope I was able to give you some ideas on what to write about. If you have any questions or concerns, please let me know! :)