There are a few tips that we have figured out after working with a lot of kids which you can use to help your child with stress.
-Schedule relaxing activities: Sometimes fun activity like sport and games can also become stressful and competitive.
-Reward your child's brave behaviours: It can be a small treat, praise or a hug.
-Encourage good sleep hygiene: Good be time routine can help your child to relax before sleeping.
-Help your child to deal with their emotions: This is the most important part you need to help your child, with how to deal with their emotions.
This can also be done by taking outside help to make your child be more emotionally intelligent. Which will allow them to manage their emotions better. Hence experiencing less stress.