This is the assessment paper that I use for my students when they first start with me. This also contains the answers in a separate section.
It covers the foundations of KS3 maths such as addition, subtraction, multiplication, division, negative numbers, estimation, etc.
I have designed this myself based on the areas of weakness that most students tend to show, even good students.
Please feel free to use this resource for your own children to identify any areas to improve.
Maths Genie website is a great free resource for maths.
It breaks maths down by grade topic and exam boards.
It has learning videos, practise papers, and past papers with solutions.