I have taught KS3/4/5 mathematics for over 15 years. More recently I have been a team leader for marking the GCSE higher statistics papers, and have been marking them for 6 years. I base my resources around exam questions and what is expected, and try to model examples and worksheets around the types of questions they may come across, while still leaving the actual questions untouched for you to use as you wish. The occasional error can crop up, and I am quick to edit them.