Never skip leg day
This hack is for you if you like using skirts or if they are part of your school uniform. You can write the answers to a test on your leg up to the point where your skirt will cover it all up. You will only need to move your leg around during the exam until the answer reveals itself.
Who would have known that your thigh was an excellent place to hide information? You will need to be extra cautious not to make your methods too obvious to avoid putting your teacher in an awkward situation. You now know to dress accordingly to a school test.