mdi child form is not maximized

I have created a mdi parent form and a mdi child. i have set the properties of the mdi child:

WindowState = Maximized
MaximizeBox = false
MinimizeBox = false

When i open the form child it is not in its Maximized size but in its normal size, yet the minimize, restore and close buttons are in the top below the menu bar of the parent form. The button minimize is disabled but not the restore button.

When i open a second child form (another instance of the form child) it´s opened in a maximized state and size too but with the buttons in the same state as the first child form.

When i open a third form (maximized) and i close it again the se secon form is restored to its normal size.

What i want is to open the mdi childs always in maximized state, the button restore always to be deactivated and when i close the top child form the others that are open not to be restored to they normal size.

Can anyone help me?

Thank you.