Hey guys, I was in a similar boat when commencing yr 11, so I'll give you some tips that I learnt along the way.
Staying physically organised -
At school -
I carried a single folder (2-Ring), and I used coloured tabs to differentiate between my different subjects.
At home -
- I had a separate folder for each subject at home (Arch-Lever) for each subject, and typically bought more for subjects like maths.
- I would do all my notes on a single day, normally Saturday morning but I shifted to Friday night later on as I preferred starting my weekend with homework and study rather than note taking. Side note; I made/make my notes on google docs as I find it easier and faster than hand writing, which I save later as a study method.
Staying mentally organised
To Do List -
These are amazing, I always have one almost every day of my life. These can be as simple as a piece of paper listing all the activities that you need to do, school and non-school related. Additionally, you can use a application such as: todoist, Microsoft To-do, wunderlist etc
Best of luck