Give them attention!!!
We all know how busy life can get, but try to carve out some time for just you and that child to have some alone time together once a week. It doesn't have to take an hour from your day. Maybe just take them to get ice cream. Ask if they want to go on a drive, or a walk around the block. Play a quick board game with them. Something that tells them "I love you, and you are important to me". One on one time with children is vital, especially if they are struggling in any way at home or school.
One on one time will help the child feel secure, and not feel the need to act out to get your attention. They're going to get your attention either way, wouldn't you rather it be positive than negative?