Does after-school work affect school performance?

Sometimes yes and sometimes no. It all depends on things like how much stress you are going through, how much work you have, and how late you must stay awake working at night. If you don't get enough sleep before the morning you may not be able to focus and get a quality education. Hope this helps. Good luck! 

At times yes but if you focus on what u want in life in the future nothing will stop you from striving for what you want