This medication can be used for children population, too, but they aren't dosed as adults (if the child weights 40 kg or more should be dosed according to the adult recommendations, also, the amoxicillin/clavulanate potassium 250-mg tablet should not be used until the pediatric patient weighs at least 40 kg or more).
If your child has an allergy history to amoxicillin, clavulanate potassium, any penicillin, the medicine shouldn't be used.
It is very important this medicine to be recommended from a physician, since the cause for sore throat can be viral (antibiotics don't work on viruses)
If the sore throat is due to viral nature (mononucleosis) the used medicine will cause generalized rash and the medicine should be stopped.
Common cold virus, and other viruses can cause the same condition.
Apo-amoxiclave will work for sore throat, only if it is caused by bacterium, but, this could be known only if a throat swab is done.

Best wishes!