Code:
var myXML:XML;
var stX:Number = stage.stageWidth;
var speedX:int = 2;
var gap:int = 20;
var index:int = 0;
var len:int;

var myLoader:URLLoader = new URLLoader();
myLoader.load(new URLRequest("schoolMessages.xml"));
myLoader.addEventListener(Event.COMPLETE, processXML);
myText1.autoSize = TextFieldAutoSize.LEFT;
myText2.autoSize = TextFieldAutoSize.LEFT;

function processXML(e:Event):void {
        myXML = new XML(e.target.data);
        len = myXML.saying.length();
        myText1.text = myXML.saying[index++].toString();
        index = (index == len) ? 0 : index;
        myText2.text = myXML.saying[index++].toString();
        index = (index == len) ? 0 : index;
        myText1.x = stX;
        myText2.x = myText1.x + Math.max(stX, (myText1.width + gap));
        myText2.y = myText1.y;
        stage.addEventListener(Event.ENTER_FRAME, mover)
}
function mover($e:Event):void {
        myText1.x -= speedX;
        myText2.x -= speedX;
        if (myText1.x <= 0 - myText1.width) {
                myText1.x = myText2.x + Math.max(stX, (myText2.width + gap));
                myText1.text = myXML.saying[index++].toString();
                index = (index == len) ? 0 : index;
        }
        if (myText2.x <= 0 - myText2.width) {
                myText2.x = myText1.x + Math.max(stX, (myText1.width + gap));
                myText2.text = myXML.saying[index++].toString();
                index = (index == len) ? 0 : index;
        }
}