Cant place symbols ABOVE scrolling BG

Question

ok, so my prof provided a rough as3 code for a scrolling bg, which i got to work fine, but when i place a symbol on the stage and test the movie, my symbol is underneath my scrolling background (by underneath i mean a layer below, NOT vertically underneath) and i can only see it because there is some transparency in my scrolling backgrounds.
to me, simply placing the symbols in a layer above the layer with the scrolling bg code should be enough, but that does nothing. 
this seems simple.  my project was due yesterday.  help.  

Answer 1

the bg consists of three .png images converted to symbols and have action script linkage (names: Base, Medium, Big).  the BGs are tied to the timeline via action script in the very first frame of the bottom-most layer.  the symbols I would like to be on top of the BGs are each on their own layer above.
also, the scrolling bg cancels any animation i apply to my symbols.
the code i am using (some of the code refers to a function i am not using; cursor placement affecting scroll direction, etc.)
stop();
//Variable to set whether the loop is Based on cursor or simply continuous
var cursorBased = false;
//Variable to determine if the continuous loop moves to right or left
var moveToRight = true;
//Variable to keep track of speed of animation
var dx = 1;
var dx2 = 3;
var dx3 = 2;
function checkCursor() {
if (cursorBased) {
if(mouseX>400 ) {
moveBG(Base1, Base2, Base3, -dx);
moveBG(Medium1, Medium2, Medium3, -dx2)
moveBG(Big1, Big2, Big3, -dx3);
if (mouseX< 50){
moveBG(Base1, Base2, Base3, dx);
moveBG(Medium1, Medium2, Medium3, dx2)
moveBG(Big1, Big2, Big3, dx3);
else if (moveToRight) {
moveBG(Base1, Base2, Base3, dx);
moveBG(Medium1, Medium2, Medium3, dx2);
moveBG(Big1, Big2, Big3, dx3);
else {
moveBG(Base1, Base2, Base3, -dx);
moveBG(Medium1, Medium2, Medium3, -dx2);
moveBG(Big1, Big2, Big3, -dx3);
//Variables that hold instances of the movieClip city
var Big1 = new Big();
var Big2 = new Big();
var Big3 = new Big();
//keeps track of which instance is on the stage
var currentBig = Big2;
//place the instances on the stage
Big1.x = Big2.x - Big1.width;
Big2.x = 0;
Big3.x = Big2.width;
Big1.y = 0;
Big2.y = 0;
Big3.y = 0;
//Variables that hold instances of the movieClip city
var Medium1 = new Medium();
var Medium2 = new Medium();
var Medium3 = new Medium();
//keeps track of which instance is on the stage
var currentMedium = Medium2;
//place the instances on the stage
Medium1.x = Medium2.x - Medium1.width;
Medium2.x = 0;
Medium3.x = Medium2.width;
Medium1.y = 0;
Medium2.y = 0;
Medium3.y = 0;
//Variables that hold instances of the movieClip city
var Base1 = new Base();
var Base2 = new Base();
var Base3 = new Base();
//keeps track of which instance is on the stage
var currentBase = Base2;
//place the instances on the stage
Base1.x = Base2.x - Base1.width;
Base2.x = 0;
Base3.x = Base2.width;
Base1.y = 0;
Base2.y = 0;
Base3.y = 0;
//display instances on the stage
addChild(Base1);
addChild(Base2);
addChild(Base3);
//display instances on the stage
addChild(Medium1);
addChild(Medium2);
addChild(Medium3);
//display instances on the stage
addChild(Big1);
addChild(Big2);
addChild(Big3);
addEventListener(Event.ENTER_FRAME, scroll);
function scroll(evt:Event):void {
checkCursor();
currentBig = tileBG( currentBig, Big1, Big2, Big3);
currentMedium = tileBG( currentMedium, Medium1, Medium2, Medium3);
currentBase = tileBG( currentBase, Base1, Base2, Base3);
function moveBG( bg1, bg2, bg3, dx ):void
bg1.x += dx;
bg2.x += dx;
bg3.x += dx;
function tileBG ( currentBG, bg1, bg2, bg3) {
if(currentBG.x < - currentBG.width) {
   if(currentBG == bg2) {
   bg1.x = bg3.x+ bg3.width;
   currentBG = bg3;
   else if( currentBG ==bg3) {
   bg2.x = bg1.x + bg1.width;
   currentBG = bg1;
   else if ( currentBG == bg1) {
   bg3.x = bg2.x + bg2.width;
   currentBG = bg2;
if(currentBG.x > currentBG.width) {
if(currentBG == bg2) {
bg3.x = bg1.x - bg1.width;
currentBG =bg1;
else if (currentBG == bg3){
bg1.x= bg2.x - bg2.width;
currentBG = bg2;
else if (currentBG == bg1) {
bg2.x = bg3.x -bg3.width;
currentBG =bg3;
return currentBG;
I am pretty much a beginner so any advice in non-intermediate/non-expert lingo would be very very very much appreciated.  Thanks in advance for any help!