the problem i am facing is that the buttons on the parent form are coming on the top of the child forms and not hiding behind

Hello, I am working on a windows application in C#.NET 2.0. I am using an MDI form with multiple buttons on it. Clicking on the buttons opens a child form. Now, the problem i am facing is that the buttons on the parent form are coming on the top of the child forms and not hiding behind. I need the child form to cover the controls on the MDI form. Would appreciate if someone can guide me in the correct direction.