Hi,
To control your son's blood sugars it will be necessary to use a combination of medications, diet and exercise.
Is he taking basal-bolus insulin? ie. different short and long acting doses?
If he is then you need to arrange to do basal testing and then also to work out his carb to insulin ratio. This is quite complex and it may be helpfyul you have a diabetes educator to work with. Alternatively, there are some very good books that can help on this. Some are Úsing Insulin, by John Walsh, and "Think Like a Pancreas".
Reducing the amount of carbs your son eats will also make blood sugar control easier. The carbs are replaced with healthy fats and proteins. The carbs that are eaten mainly come from vegetables, with very little from sugars or refined sources.
I am assuming that your son is young; there is a group called type 1 grit that may be a good resource.
Med help also has some apps which are sugar monitoring and food diary that may be helpful.
Please come back and let us know how you are going, and if we can offer further support.