When is your kid faking it ?
Children may be small, and they seem naive, but don't be fooled every time they say they are not feeling well.
In case you have a small child ( age 4 or 5 ) it may be the case, but if you're having a kid who is going to elementary school or is even older, they will lie to you sometimes, in order to avoid school.
If you are not sure if your kid is faking or not, you should always tell him/ her, that he should go to school, but that he/she must know that in case they don't feel well, they can always come home.
Sometimes the problem your kid is having can be a lot bigger then we think. We usually think they don't want to go because they want to avoid a school test, but that doesn't have to be the case.
So before you start making any decision, ask them if anything is bothering them, because in a lot of cases kids are being molested, and they don't want to talk about that probably because they are either afraid or too shy to say.
If you talked to him/ her, and you figured out that they are not lying, these are the cases when you should keep them at home : If they are vomiting or having a diarrhea, if they are having a fever ( this is a serious thing, and it will only get worse if they are not at home ), if they are having skin rashes, etc.