Hello serena,
Anyone can have headaches. Headaches are not a symptom of SZ. People diagnosed with SZ, and people without SZ, can have headaches.
There is such a thing as childhood schizophrenia, which I believe is rare yet is possible. If your son or daughter or other loved one is hearing voices at 7 years old, I would investigate and research a qualified professional, if necessary a psychiatrist, to do a complete evaluation, including blood test to rule out another medical condition that is not SZ and can cause someone to hear voices.
When it comes to treating young children with medication, different people have different opinions on the use of these drugs for children. So if you are experiencing this, I would ask you to research the situation, get informed and educate yourself so you can be OK with whatever decision you make.
Best regards,
Christina