An allergic reaction or another kind of contagious rash will definitely keep you home.  First, scratch your chest lots until it's bright red. Try to keep a circular pattern to make it look more realistic. Finally try to combine the "rash" with something else like a runny nose or a headache. If you do a good job at seeming sick, your parents will probably want to take your temperature. Be ready, though, to act quickly and fake having a fever.  Ask to go to the bathroom before they take your temperature. Make sure you have a cup with you. Fill it with warm water to drink and rinse through your mouth, especially under your tongue. This will raise the temperature of your mouth. Be sure to flush the toilet before you turn on the sink, just so your parents don't get too suspicious! Note: this only works if they check it under your tongue, obviously.  If the thermometer is one that goes in your ear, try to get it before your temperature's taken and hold it to something warm, like a radiator or a light bulb. If your parents are the kind that just feel your forehead, frequently rub it rapidly when they're not looking, or take a blow dryer and heat your face and say your forehead feels warm.  Put warm water in your armpits, forehead, and cheeks. It makes you warm and looks like you have been sweating. You’re aiming for a temperature that is above 99 degrees (37 Celsius) but lower than 103 degrees (39.4 Celsius). If it's below 99 degrees then it doesn't count as a fever, if it's 103 degrees you'll likely be taken to the doctor's right away. It's very easy to fake a migraine because there's no way of knowing if you're telling the truth or not. By just faking the symptoms, your parents will believe you.  Light and most sounds should bother you. Pretend you're annoyed by them. Say that only one specific area of your head hurts, for example over your right eyebrow. This is essential if you want to fake a migraine. Touch your forehead every now and then and frown when doing so. Say that you feel dizzy and can't see very...

TL;DR in Indonesian:
Berpura-pura mengalami ruam. Berpura-pura demam. Berpura-pura migrain. Berpura-pura diare. Berpura-pura sakit mata. Berpura-pura sakit perut, mual, atau kram. Berpura-pura masuk angin atau flu. Berpura-pura sakit tenggorokan.