Map issue

[Tinnin]

Hi all.
This regards "Accelerated C++" Exercise 7-2.
I'm trying to write a program that uses a map to put students grades into grade bands and print which band each student falls into.
The grade bands are (A: 90-100, B: 80-89.99, C: 70-79.99, D: 60-69.99, F: <60).

I'm getting into a bit of a mess with it and I can't see where or why exactly?

My program is as follows:

#include "Student_info.h"

#include <vector>
#include <map>

using std::cin;     using std::vector;      using std::cout;
using std::endl;    using std::map;         using std::string;

int main()
{
    vector<Student_info> students;

    Student_info student;

    char A, B, C, D, E, F;

    map<char, vector<string> > bands;

    while(read(cin, student))
    {
        students.push_back(student);
    }

    cout << endl;

    // Move to seperate function
    for(vector<Student_info>::const_iterator it = students.begin(); it != students.end(); ++it)
    {
        if(it->grade >= 90 && it->grade <= 100)
            bands[A].push_back(it->name);
        else if(it->grade >= 80 && it->grade <= 89.99)
            bands[B].push_back(it->name);
        else if(it->grade >= 70 && it->grade <= 79.99)
            bands[C].push_back(it->name);
        else if(it->grade >= 60 && it->grade <= 69.99)
            bands[D].push_back(it->name);
        else if(it->grade < 60)
            bands[F].push_back(it->name);
    }

    for(map<char, vector<string> >::const_iterator it = bands.begin(); it != bands.end(); ++it)
    {
        cout << it->first << ": ";

        vector<string>::const_iterator stud_it = it->second.begin();
        cout << *stud_it;

        ++stud_it;

        while(stud_it != it->second.end())
        {
            cout << ", " << *stud_it;
            ++stud_it;
        }

        cout << endl;
    }

    return 0;
}

Student_info.cpp

#include "Student_info.h"

#include <vector>

using std::istream;     using std::vector;

istream& read(istream& is, Student_info& s)
{
    is >> s.name >> s.grade;

    return is;
}

Student_info.h

#ifndef GUARD_Student_info
#define GUARD_Student_info

// Student_info header file
#include <iostream>
#include <string>

struct Student_info
{
    std::string name;
    double grade;
};

std::istream& read(std::istream&, Student_info&);

#endif

My input is:
student1
98
student2
87
student3
45
student4
67
student5
56
student6
72

My ouput is:
: student1, student6
3: student2
m: student4
w: student3, student5

I want it to be:
A: student1
B: student2
C: student6
D: student4
F: student3, student5

Where am I going wrong?
It's my first time using maps. I figured I'm screwing up with the key but I don't know what I'm doing wrong.

Thanks in advance for any help offered.

[mrnutty]

Initialize you letter grades.

 char A('A'), B('B'), C('C'), D('D'), E('E'), F('F');

[Tinnin]

Wow. I'll just pretend I never made that mistake. This post never happened ;P.
Cheers firstPerson :)