How to access a variable from another C# script in Unity

I am working on a simple game project, and have a problem. The problem is accessing the variable from one script to another.

For example :-

I have 2 Scenes (Game Scene and Game Over Scene), Game Scene has a Player Game Object , who has a int Variable Score.

using UnityEngine;
using System.Collections;

public class Game_Scene_Script : MonoBehaviour 

{
     private int Score ;

     // Use this for initialization
     void Start () 
     {
          Score = 0 ;
     }

     // Update is called once per frame

     void Update () 
     {
          // Let us assume some one played the game
          // And Now the Score is 207
          Score = 207 ; 
     }
}

Now I want to access that int Variable Score in Game Over Scene which a Game Object.

So how can I access that int Variable from that script?

I searched for, but couldn't find any proper answer I wanted. Even-though some answers are in JavaScript , some are in Unity 4.x etc.