Exception in thread main error when trying to fill in a 2D array in column major form java

Code:

import java.util.*;
public class lab3 {
public static void getScores(int[][] matrix){ 
Scanner kb = new Scanner(System.in);
int r, c;
for (c = 0; c < matrix[0].length; c++){
   for (r = 0; r < matrix.length; r++) 
       System.out.println("enter scores for test "+(c+1)+ " and student "+(r+1));
    matrix[r][c] = kb.nextInt(); 
} 
kb.close();
}
public static void printArray(int[][] matrix) { 
for (int c = 0; c < matrix[0].length; c++)
    for (int r = 0; r < matrix.length; r++){ 
        System.out.printf("%5d", matrix[r][c]); 
        System.out.println(); 
    } 
}
public static void main(String[] args){
Scanner kb = new Scanner(System.in);
System.out.println("how many students are there?");
int students=kb.nextInt();
System.out.println("How many tests are there?");
int tests=kb.nextInt();
int [][] grades= new int [students][tests+1];

getScores(grades); 
printArray(grades);

I feel like I'm close but I keep getting an error. filling an array in column major form is the main deal so "get scores" method and the declared array at the bottom is where I think my problem is please help me