I saw a great thing on anger with younger kids. They talked to the kids about how when we are angry, is comes out in our hands, feet and mouths, so when we are angry we want to hit, kick and shout.
When the child is calm, you come up with a tool box of safe and OK ways to let the anger out of our feet, hands and mouths. It works best when they come up with the ideas themselves.
Ideas could be - hitting a pillow/teddy, running up and down stairs, stomping my feet, ripping newspaper, banging the sofa with my hands, singing instead of shouting, finding acceptable words to shout (I am cross, cross cross! instead of I hate you) Then when you see them get angry, you acknowlegde their anger (this is important, the anger is real) and remind them to use their toolbox to let the anger out.
While it might be SEN /masking etc, lots of children melt down over parents after being good all day at school. It is especially common when they are younger.