TM4T recommends that, as far as possible, lesson resources are stored electronically in preference to paper.
This means that you should scan as much material as you can as soon as you can, and store the material electronically.
However, some paper resources are inevitable in most subjects, so you are likely to need a second box file, labelled with your name eg Mr Bigrush Lesson Resources. The longer-term answer, though, is to scan everything.