Problem with increasing a variable

I have a problem with increasing an integer variable (level) by one. I think, I know where the problem is, but I do not know how to fix it. I explain my problem in code:

Let's say, I have two classes, Game.js and Menu.js.

In menu class I have a detection for buttons, like play, score and so. After score button is clicked, I call a function from game class. The function increases my level variable (there is a line: level++), but it does not increase it by one, but by two times. It performs a given piece of code twice, but I clicked just one time.

Then I try to put the function in menu class, and there it performs just one time, if I wanna. Of course, in Hierarchy have game objects with both classes. Here is sample of code:

Menu.js

 //declare the raycast objects here so we dont need to instantiate them each frame
 private var ray        : Ray;
 private var rayCastHit : RaycastHit;
 
 var game : Game;        // instantiate class Game.js
 
 var play : GameObject;  // play button
 var score: GameObject;  // score button
 var exit : GameObject;  // exit button
 
 function Start()
 {
 }
 
 function Update()
 {
     var aniPlay : aniSprite = GetComponent("aniSprite");
 
     if(Input.GetMouseButtonDown(0))
     {
         ray = Camera.main.ScreenPointToRay(Input.mousePosition);
         
         if(Physics.Raycast (ray, rayCastHit))
         {
             if(rayCastHit.transform.name == "playButton" && !variables.drawAbout)        
             {
                 Application.LoadLevel("GameScene");
             }
             if(rayCastHit.transform.name == "scoreButton" && !variables.drawAbout)        
             {
                 game.write();
             }
             // here is more button detections, but this is just a sample
         }
     }
 }

Game.js

 function Start()
 {
 // in my original code, I give here valus to variables
 }
 
 function Update()
 {
 }
 
 function write()
 {
     // Here is the root of the problem, this log will be write twice, but I want to only one time, 
     // because I have here the level variable and this increase it twice, not one time 
     Debug.Log("this log will be write twice");
 }

If I have given the function write() to class Menu.js, all have been right, but I can't give every funtion to one class, it would be such mess. Please, help me, I really do not know, how to increse the variable of another class via a function only once.