Children are affected by many different types of headaches, and they can range in severity from a mild ache to severe pain. Headaches in children cause problems in approximately 20% of all children between the ages of 5 and 17, according to The National Headache Foundation (NHF) at headaches.org. 
These kids and teenagers experience headaches at least 15 days per month.
This translates into approximately 10.3 million kids in the US alone.
What about other cultures, headaches do not discriminate between cultures.
These US statistics both astound and horrify me.
What are we doing about it?
Most studies say more research is needed. Using the US statistics, most children will experience at least one headache by the time they graduate high school, and the odds go up if there is a family history of neurological disease or migraines.
It's important to know the classifications to effectively treat the causes of headaches in children.
Headaches are thought of as primary headaches and secondary headaches.
These classifications are Primary or Benign and Secondary.
As I mentioned, children are affected by many different types of headaches that can range from a mild headache or stomach ache to severe pain.
Here is what tension type headache symptoms look like:
Migraine headache symptoms are:
I've written more about that here - Migraine Symptoms In Children: How They Differ To Adults.
Stress at school, in family dynamics, or from friends can be a trigger, so it might be necessary to talk to your child about other emotional factors that may be causing them stress or upset.
Boys are more likely than girls to have headaches (and migraines) before the age of ten (before puberty).
When a diagnosis is from secondary causes of headaches in children, this means a viral and bacterial infection could be the cause of the headaches. It could be from dehydration or something more serious like a tumor or intracranial bleeding.
If you suspect any other cause or if new or sudden symptoms
accompany the headache, like: fever, exhaustion and stiff neck, "your child could have meningitis or encephalitis and you should seek medical attention immediately." 
The doctor will do tests to rule out other more serious causes like: pressure around the brain, brain tumors, infections or blood clots.
Some other symptoms to watch for are: nausea, vomiting,
clumsiness, muscle weakness, seizures, and personality changes.
Causes of headaches in children are different to triggers.
The current theory of what causes migraines involves the blood vessels and a chemical reaction. Briefly, it's likely to happen when blood vessels in the head and neck spasm or constrict and then minutes to hours later, the blood vessels dilate. When they dilate, they get larger and fill with blood, which causes more pressure in the skull and a headache develops.
Triggers cause the reaction throwing the body off balance and into headache or migraine. Here's a list of potential triggers:
*And after puberty girls get more migraines than boys, so the obvious causes of headaches in children of this age are hormones.
Some headaches can be serious, so if you are concerned, please see your physician asap. You and your child should see the doctor if:
Also, as these symptoms are NOT common with headaches in children, please be aware of: numbness or paralysis, difficulty speaking
or confusion, and any personality changes. 
includes lethargy, being indifferent, apathetic, or sleeping too much. I
realize this may look like the normal teenager, so, I mean more so to
watch for personality changes linked to having a migraine episode the
The most effective medicines for headaches in children according to Migraines for Dummies are ibuprofen or acetaminophen.
It is also recommended to be aware of any emotional side effects and or stressful factors affecting your child.
It might be necessary to talk with them about it all, or find the help of a professional school counselor or a counselor that works specifically in your child's problem area.
I can recommend getting extra support from a professional pain counselor, there should be one at their school.
Stress is one of the causes of headaches in children, so teach your child some good relaxation techniques. Here are a couple I use:
If your child is quite young, drawing a picture of their migraine can help you see more of their symptoms.
They will often have trouble
linking nausea or vomiting to the migraine or pain, and the throbbing
pain we are familiar with as adults is more typically dull and across
their forehead. 
According to the National Headache Foundation (NHF) these five simple things can help reduce and avoid headaches:
#1. Keep eating times regular and form healthy habits. There is
significant research that proves that many children have fewer and less
distressing attacks after routine and a sense of regularity is
#2. Stay hydrated. Dehydration can trigger headaches. So this means water, not sugary sodas or caffeinated drinks.
Water - sipped
slowly every 15 minutes is more effective than throwing down a whole
glass in one go. Homemade drinks are best where you can control the
sugar dose – lemonade from real lemons. An apple is also like having a
glass of water. Sorry, but I do not recall where I read that one!
#3. This one almost goes without saying, but, limit caffeine and sugar consumption.
#4. Keep TV watching and computer usage to a minimum, especially one hour before bed.
#5. Keep regular sleeping times and perform sleep rituals, form habits for a healthy winding down and going to sleep routine.
Causes of Headaches in Children References:
1. National Headache Foundation (2011) Children experience frequent headaches [Online], Available at: http://www.headaches.org /blog/children-experience-frequent-headaches. Accessed Feb. 2016.
2. Stafford, D. and Shoquist, J. MD. (2003) Migraines for Dummies. Wiley Publishing, Inc: New York. p.243.
3. Marcus, Dr. Dawn A. (2006) 10 Simple Solutions to Migraines: Recognize triggers, control symptoms and reclaim your life. New Harbinger Publications: CA. p. 14.
4. Migraine Headaches (2010) When to worry about your child’s headaches [Online], Available at: http://www.webmd.com/migraines-headaches. Updated Dec 2018.