Compass: may have to draw circles or arcs to show constructions.
Protractor: may have to draw angles (e.g. to draw pie chart)
Set Square: may need it for constructions.
Calculator: (be sure it is an allowed type and know how to use it well before the day of the exam)
Highlighter: (Optional, not for use on exam answer sheet but can be useful in some exams to mark off the bits of questions on the exam paper as you complete them, so that if there are any you need to come back to towards the end of the exam time you do not miss them.
Blue or black biros x 3. You will be writing for a few hours so a pen could run out of ink. It might leak. Test them before you leave home. If you just grab a few biros from home that have not been used for a long time they might not work.
Pencils x 2. Better to bring an extra pencil than to have to spend precious time sharpening one that the top breaks on . HB pencils for drawing diagrams on graph paper.
Coloured Pencils: not compulsory but good idea to bring three or four coloured pens or pencils to make sketches/diagrams clearer. Do not use pencils with very soft lead as they are prone to break and may not stand out enough on exam answer sheet. Do not use markers that could show through to other side of page.
Topper (Pencil sharpener): just in case tops of all pencils break. You might be over anxious and press too hard causing the tops to break.
Rubber/eraser to rub out any mistakes in diagrams.
Watch with hour and minute hands in case sitting where can not see clock, so can keep track of time spent on each question compared to what you had planned.
Have a convenient pencil case or container to hold all of the above so that you do not have to go searching for individual items before each exam, and possibly forget something.
Remember, you will be able to get a copy of the “Tables and Formulae” booklet during the exam. If they are not given out to everyone before the exam begins, ask for them straight away, so that you do not have to interrupt your concentration and waste time attracting the attention of a supervisor to get one later.