import os
import sys
from io import BytesIO, IOBase
def main():
t = int(input())
for _ in range(t):
n, k = read_ints()
s = input()
if n < 2 * k + 1:
print('NO')
else:
for i in range(k):
if s[i] != s[n - i - 1]:
print('NO')
break
else:
print('YES')
BUFSIZE = 8192
class FastIO(IOBase):
newlines = 0
def __init__(self, file):
self._file = file
self._fd = file.fileno()
self.buffer = BytesIO()
self.writable = "x" in file.mode or "r" not in file.mode
self.write = self.buffer.write if self.writable else None
def read(self):
while True:
b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
if not b:
break
ptr = self.buffer.tell()
self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
self.newlines = 0
return self.buffer.read()
def readline(self):
while self.newlines == 0:
b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
self.newlines = b.count(b"\n") + (not b)
ptr = self.buffer.tell()
self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
self.newlines -= 1
return self.buffer.readline()
def flush(self):
if self.writable:
os.write(self._fd, self.buffer.getvalue())
self.buffer.truncate(0), self.buffer.seek(0)
class IOWrapper(IOBase):
def __init__(self, file):
self.buffer = FastIO(file)
self.flush = self.buffer.flush
self.writable = self.buffer.writable
self.write = lambda s: self.buffer.write(s.encode("ascii"))
self.read = lambda: self.buffer.read().decode("ascii")
self.readline = lambda: self.buffer.readline().decode("ascii")
sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
input = lambda: sys.stdin.readline().rstrip("\r\n")
def read_ints():
return [int(c) for c in input().split()]
def print_int_lines(lst):
print('\n'.join(map(str, lst)))
if __name__ == "__main__":
main()
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <string.h>
#include<bitset>
#include<cmath>
#include<algorithm>
#include<iomanip>
#include<vector>
#include<stack>
#include<queue>
#include<deque>
#include<set>
#include<map>
#include<string>
#include<cstdlib>
#include<sstream>
#define endl '\n'
#define all(x) (x).begin(), (x).end()
#define pb push_back
#define test_case int t;cin>>t;while(t--)
typedef long long int ll;
typedef long double ld;
using namespace std;
void Abdo_Saad() { std::ios_base::sync_with_stdio(0);cin.tie(NULL);cout.tie(NULL); }
ll gcd(ll a, ll b) { return(b == 0 ? a : gcd(b, a % b)); }
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
void set_bit(int& n, int idx) { n |= 1 << idx; }
void reset_bit(int& n, int idx) { n &= ~(1 << idx); }
void flib_bit(int& n, int idx) { n ^= 1 << idx; }
bool pal(string s)
{
int n = s.size();
for (int i = 0;i< n/2;i++)
{
if (s[i] != s[n - i - 1])return false;
}
return true;
}
void solve()
{
int n, k;
cin >> n >> k;
string s;
cin >> s;
if (!k)
{
cout << "YES\n";
return;
}
if (2 * k == n)
{
cout << "NO\n";
return;
}
string t1, t2;
for (int i = 0;i < k;i++)
{
t1.push_back(s[i]);
t2.push_back(s[n - i-1]);
}
reverse(all(t2));
if (pal(t1 + t2))cout << "YES\n";
else cout << "NO\n";
}
int main()
{
Abdo_Saad();
test_case
solve();
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