OnCollisionEnter Won't Edit Other Variables

Alright, so I have created a little racing game. I was making a checkpoint, so that you couldn't cross the finish line and get a lap without passing the checkpoint. At first I just wanted it to be an OnTriggerEnter, which worked fine. But in 2 player, that wouldn't work. I have 3 scripts (1 for the finish line, 1 for the checkpoint for P1, and 1 for the checkpoint for P2), and when I pass the checkpoint, it won't edit the variables! Here's the script for the checkpoint for P1:

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
  
 public class Checkpoint : MonoBehaviour {
  
  
     public Text Checker;
 public Text Reseter;
     private int checkpoint;
 private int checkreset;
  
     // Use this for initialization
     void Start () {

         Checker.text = "0";
         checkpoint = 0;
 
  
     }
  
  
     // Update is called once per frame
     void Update () {

     if(Reseter.text == "1"){
         checkpoint = 0;
     }
         

     if(checkpoint == 1){
         Checker.text = "1";
     }


     }
  
  
     void OnCollisionEnter (Collision col) {
         if(col.gameObject.name == "Player 1"){
         checkpoint = 1;
             Reseter.text = "0";
         }
  
     }

  
      
  
 }
  

And for P2:

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
  
 public class Checkpoint2 : MonoBehaviour {
  
  
     public Text Checker2;
 public Text Reseter2;
     private int checkpoint;
 private int checkreset;
  
     // Use this for initialization
     void Start () {

         Checker2.text = "0";
         checkpoint = 0;
 
  
     }
  
  
     // Update is called once per frame
     void Update () {

     if(Reseter2.text == "1"){
         checkpoint = 0;
     }
         

     if(checkpoint == 1){
         Checker2.text = "1";
     }

     }
  
  
     void OnCollisionEnter (Collision col) {
  
         if(col.gameObject.name == "Player 2"){
     checkpoint = 1;
         Reseter2.text = "0";

     }
  
     }

  
      
  
 }

Here's the script for the Finish Line:

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
  
 public class Lap : MonoBehaviour {
  
  
     public Text MyText;
 public Text MyText2;
 public Text Checker;
 public Text Checker2;
 public Text Reseter;
 public Text Reseter2;
     private int score;
 private int score2;
 private int counter;
 private int counter2;
  
     // Use this for initialization
     void Start () {
     
         score = 0;
     score2 = 0;
     counter = 1;
     counter2 = 1;
     Reseter.text = "0";
     Reseter2.text = "0";
 
  
     }
  
  
     // Update is called once per frame
     void Update () {

         MyText.text = "Lap: "+ counter;
     MyText2.text = "Lap: "+ counter2;
         
         if(counter >= 3){
             MyText.text = "You beat the race!";            
             if(Input.GetMouseButtonDown(0)){
                 Application.LoadLevel("Menu");

             }

         }

     if(counter2 >= 3){
         MyText2.text = "You beat the race!";
     if(Input.GetMouseButtonDown(0)){
         Application.LoadLevel("Menu");
             }
        }
  
     }
  
  
     void OnCollisionEnter (Collision col) {
          if(col.gameObject.name == "P1"){
     if(Checker.text == "1"){
             score = score + 1;
             counter = score + 1;
         Checker.text = "0";
         Reseter.text = "1";
     }
     }

     if(col.gameObject.name == "P2"){
         if(Checker2.text == "1"){
         score2 = score2 + 1;
         counter2 = score2 + 1;
         Checker2.text = "0";
         Reseter2.text = "1";
     }
     }
  
     }


  
      
  
 }
  

Is there a mistake I made that doesn't show up in the editor? Thanks in advance.