Unity/C# Respawn and score Problem

So I'm using Unity and C# and am currently getting a problem where the ball doesn't respawn and the score goes up continuously. I'm not sure if this is a coding error or just a unity error. The score thing came up after i put the Paddle Obj on the score script in the deadzones.

This is the coding I'm using:

using UnityEngine; using System.Collections;

public class Score : MonoBehaviour {

 public TextMesh currSco;
 public GameObject ballPref;
 public Transform paddleObj;

 GameObject ball;
 int score;

 void Update () 
 {
     ball = GameObject.FindGameObjectWithTag("Ball");
     currSco.text = "" + score;
 }
 void OnTriggerEnter(Collider other)
 {
     if (other.tag == "Ball")
     {
         score += 1;
         Destroy(ball);
         (Instantiate(ballPref, new Vector3(paddleObj.transform.position.x + 2, paddleObj.transform.position.y,0), Quaternion.identity) as GameObject).transform.parent = paddleObj;

     }
 }
 

}

And this is the Tutorial I'm using: https://www.youtube.com/watch?v=0YLDzKkXlME

Can someone help? If you guys need anything else feel free to ask.