For a lot of children anger is a sign of sadness or anxiety. Although they may not always be able to explain how they feel, it may be worth looking at the pages on anxiety and low mood as well. Anger and aggressive behaviour can be hard to cope with, both for the child themselves and for those around them. These resources give some advice.
Other sources of help can be found in the Parents Survival Guide.
Responding to Anger in Children -video from "the Parents Lounge at YoungMinds
What to Do When your Temper Flares : A Kid’s Guide to overcoming problems with Anger.
by Dawn Huebner. Workbook with lots of metaphors and useful strategies. Good for age 6-12 years. Available Here.
Volcano in My Tummy: Helping Children to Handle Anger
by Elaine Whitehouse. Useful for parents and teachers. Helping children to deal with frustration and anger in more constructive ways while acknowledging that it's OK to feel angry. Available here
This NHS page has advice on helping your child cope with anger and helping you work out why your child might be feeling that way. Available Here.
How to cope with anger and aggressive behaviour
How to defuse situations and avoid making them worse and how to look after yourself. There is a good video too. Available Here.
Parents guide on how to respond to anger
Advice on dealing with aggression and violence. Available Here.
There are no specific Apps for anger management but many Apps that can help children and young people to relax (see Anxiety section)