Error #1009

Hello! I have a LevelSelecMenu clip which shows menu, where you have to choose a level to play, when you click on the Level 1 button, it loads Level 1. I need to delete Level1 from stage(if level is done), but I have an Error #1009. Please help me to figure out the problem.

LevelSelecMenu

package {
    import flash.display.MovieClip;
    import flash.display.SimpleButton;
    import flash.events.MouseEvent;
    
    public class LevelSelectMenu extends MovieClip {
        public static var level_1:Level_1;
        
        public function LevelSelectMenu() {
            Level_1Button.addEventListener(MouseEvent.CLICK, Level_1ButtonClick);
        }
        
        private function Level_1ButtonClick(e:MouseEvent) {
            level_1=new Level_1();
            stage.addChild(level_1);
        }
    }
}

[COLOR=#000000]
[/COLOR]
Level_1
[LEFT]

package {
    import flash.display.MovieClip;
    
    public class Level_1 extends MovieClip {
        
        public function Level_1() {
            stage.removeChild(LevelSelectMenu.level_1);
        }
    }
}

[/LEFT]