итераторами для std::set

void work_with_students(set<Student>::iterator first,
        set<Student>::iterator last)
{
    cout << "What do you want to do with students?\n";
    cout << "\t1 - rename them\n";
    cout << "\t2 - enter another age of the student\n";
    cout << "\t3 - change the mark\n";
    cout << "\t0 - do nothing\n";
    cout << "\t>>Your decision: ";
    int decision;
    cin >> decision;
    set<Student>::iterator i = first;
    int j = 0;
    switch (decision)
    {
    case 1:
    {
        string name;
 
        if (first == last)
        {
            cin >> name;
            first->setName(name);
        }
        else
            while (i != last)
            {
                cout << "new name #" << ++j << ": ";
                cin >> name;
 
/*!*/               i->setName(name); // вот здесь
            }
 
        break;
    }
    case 2:
    {
        int year;
 
        while (i <= last)
        {
            cout << "new year #" << ++j << ": ";
            cin >> year;
/*!*/           i->setYear(year); //вот здесь
        }
 
        break;
    }
    case 3:
    {
        double mark;
 
        while (i <= last)
        {
            cout << "new mark #" << ++j << ": ";
            cin >> mark;
/*!*/           i->setMark(mark);//вот здесь
 
        }
 
        break;
    }
    case 0:
    default:
        return;
    }
}
 
}

passing 'const Student' as 'this' argument of 'void Student::setName(const string&)' discards qualifiers
passing 'const Student' as 'this' argument of 'void Student::setYear(int)' discards qualifiers
passing 'const Student' as 'this' argument of 'void Student::setMark(double)' discards qualifiers

class Student
{
    string name;
    int year;
    double mark;
public:
    Student(const string & n = "Ivanov", int y = 17, double m = 4.0);
    virtual ~Student();
    Student(const Student & s);
    Student(double m);
    const Student & operator=(const Student & s);
 
    const string & getName() const;
    int getYear() const;
    double getMark() const;
 
    void set();
    void set(const Student & s);
    void set(const string & n, int y , double m);
    void setName(const string & n);
    void setYear(int y);
    void setMark(double m);
 
 
    bool operator==(const Student & s) const;
    bool operator!=(const Student & s) const;
    bool operator>=(const Student & s) const;
    bool operator<=(const Student & s) const;
    bool operator>(const Student & s) const;
    bool operator<(const Student & s) const;
 
    void show() const;
 
    friend ostream & operator<<(ostream & os, const Student & s);
    friend istream & operator>>(istream & is, Student & s);
 
};