GeometryUtility.TestPlanesAABB working strangely with parallax background 2D

Hello all I started working on a parallax background for my 2d game. Everything worked fine,except when I had to make an object pool that recycles the tiles of background that the player left behind him and move it at the opposite side of the line of background tiles(a lot of looping sprites all spawned in an array wich is backs in the code). To check if a tile is out of the camera I use GeometryUtility.TestPlanesAABB but it works stragely in fact the tiles don't change the position to go to the other side when they are out of the camera's sight but when they are in the middle,at the level of the player. Here's the piece of code with the problem:

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 public class ParallaxScroll : MonoBehaviour {
 
     public GameObject[] backs; //all the spawned backgrounds are stored here
     GameObject player;
     float focal_speed;//velocità di movimento del player da cui dipende lo scrolling
     public float[] back_speeds; //the speeds of the different layers of background based on the depth
     bambina_inputs bambina_vars=new bambina_inputs();
     BackgroundManager back_manager;
     Plane[] planes;
  
     void Start () {
         backs = GameObject.FindGameObjectsWithTag("backgrounds"); 
         player = GameObject.FindGameObjectWithTag("Player");
         bambina_vars = player.GetComponent<bambina_inputs>();
         back_manager = gameObject.GetComponent<BackgroundManager>();
         planes = GeometryUtility.CalculateFrustumPlanes(Camera.main);
     }
  foreach (GameObject back in backs)
         {
             Renderer back_renderer = back.GetComponent<Renderer>();
             //if it's out of the screen
             //DX
             if(!CheckIfInScreen(back_renderer) && back.transform.position.x<player.transform.position.x && Input.GetKey(KeyCode.RightArrow))
             {
                 MoveToTheOtherSide(back, back_manager.x_offset, back_manager.n_backs);
             
             }
             //SX
             if (!CheckIfInScreen(back_renderer) && back.transform.position.x > player.transform.position.x && Input.GetKey(KeyCode.LeftArrow))
             {
                 MoveToTheOtherSide(back, back_manager.x_offset, back_manager.n_backs);
 
             }
         }
      }
 
     //moves the object to the opposite side of the background
     void MoveToTheOtherSide(GameObject g_to_move,float x_offset,int n_tiles_to_move)
     {
         //made the casting so the Input.GetAxis return value is only 1 or -1
         g_to_move.transform.position = new Vector3(g_to_move.transform.position.x + (x_offset * n_tiles_to_move) * (int)Input.GetAxis("Horizontal"),
             g_to_move.transform.position.y,
             g_to_move.transform.position.z);
     }
     //checks if an object is in the screen
     public bool CheckIfInScreen(Renderer renderer)
     {
          bool in_screen = GeometryUtility.TestPlanesAABB(planes, renderer.bounds);
          return in_screen;
     }
 }

What's wrong? And also don't hesitate to suggest me a better way to make a parallax scrolling (I now that one sucks,I already gave a look to the one in the example project but i wasn't working good with my background).Thank you very much for your time and your help :D