My youngest is slowly working out of chaos and into order. It's a slow process in some boys, especially.
You can get him the calendars and the organizers and study supplies, but he has to have desire to use it and remember.
A teacher once suggested to us to find one special "goal" he would work for and together create a plan. Just an example: 2 weeks of remembered homework and good reports from teachers means a movie for your son and a friend over the weekend! or something like that.
Work with the teachers where he is having the most problems and let them know you are working on this at home, and you will be checking in with them to see if there is progress. Some of those teachers might have good ideas, too!!!
6th graders brains go on vacation for a while....teachers can be helpful.
Seek their help and give them a really nice Christmas gift!