Error: Too many initializers. Looking for a solution

#pragma once
#include <array>
#include <string>
#include <iostream>
#include <iomanip>
using namespace std;

class GradeBook
{
public:
    static const size_t students{ 10 };//number of students
    static const size_t tests{ 3 };//number of tests
    //two argument contructor initializes courseName and grades array
    GradeBook(const string& name, array<array<int, tests>, students>& 
       gradesArray)
        : courseName(name), grades(gradesArray)
    {

    }

    //function to set the courseName
    void setCourseName(const string& name)
    {
        courseName = name;
    }

    //function to retrieve the course name
    const string& getCourseName() const
    {
        return courseName;
    }

    //displaying a welcome message
    void displayMessage() const
    {
        cout << "Welcome to the grade book for\n" << getCourseName() << "!" 
            << std::endl;//displaying a welcome message
    }

    //perform various operations on the data
    void processGrade() const 
    {
        outputGrades();//output grades array
        cout << "\nLowest grade in the book is " << getMinimum()
            << "\nHighest grade in the grade book is " << getMaximum()
            << endl;

        outputBarChart();//display grade distritution chart
    }

    //find minimum grade in the entire gradebook
    int getMinimum() const
    {
        int lowGrade{ 100 };
        //loop thru rows of grades array
        for (auto const& student : grades)
        {
            //loop thru columns of grades array
            for (auto const& grade : student)
            {
                if (grade < lowGrade)
                {
                    lowGrade = grade;
                }
            }
        }

        return lowGrade;//return lowest grade
    }
    // find the maximum in the entire gradebook
    int getMaximum() const
    {
        int highGrade{ 0 };
        //loop thru rows of grades array
        for (auto const& student : grades)
        {
            //loop thru column of grades array
            for (auto const& grade : student)
            {
                if (grade > highGrade)
                {
                    highGrade = grade;
                }
            }
        }

        return highGrade;//return the highest grades
    }
    //determine average grade for particular set of grades
    double getAverage(const array<int, tests>& setOfGrades) const
    {
        int total{ 0 };

        for (int grade : setOfGrades)
        {
            total = total + grade;
        }

        return static_cast<double>(total) / setOfGrades.size();
    }
    //output bar chart displaying grade distribution
    void outputBarChart() const
    {
        int testNumber = 0;
        cout << "\nOverall grade distribution:" << endl;

        const size_t frequencySize{ 11 };
        array<unsigned int, frequencySize> frequency{};

        for (auto const& student : grades)
        {
            for (auto const& test : student)
            {
                testNumber = ++frequency[test / 10];
                cout << endl << testNumber << endl;

            }
        }

        for (size_t count{ 0 }; count < frequencySize; ++count)
        {
            if (0 == count)
            {
                cout << " 0 -9:";
            }
            else if (10 == count)
            {
                cout << " 10:";
            }
            else
            {
                cout << count * 10 << "-" << (count * 10) + 9 << ": ";
            }

            for (unsigned int stars{ 0 }; stars < frequency[count]; ++stars)
            {
                cout << '*';
            }

            cout << endl;
        }
    }
    //for each grade frequency, print bar in chart
    void outputGrades() const
    {
        cout << "\nThe grades are:\n\n";
        cout << "            ";

        for (size_t test{ 0 }; test < tests; ++test)
        {
            cout << "Test " << test + 1 << " ";
        }

        cout << "Average" << endl;

        for (size_t student{ 0 }; student < grades.size(); ++student)
        {
            cout << "Student " << setw(2) << student + 1;

            for (size_t test{ 0 }; test < grades[student].size(); ++test)
            {
                cout << setw(8) << grades[student][test];
            }

            double average{ getAverage(grades[student]) };

            cout << setw(9) << setprecision(2) << fixed << average << endl;
        }
    }
private:
    string courseName;
    array<array<int, tests>, students> grades;
};

Source file

//Creates GradeBook object using a two-dimensional array of grades
#include <array>
#include "GradeBook.h"//GradeBook class definition
using namespace std;

int main()
{
    //two dimentional array of student grades
    array<array<int, GradeBook::tests>, GradeBook::students> grades{
        {87, 96, 70},
        {68, 87, 90},
        {94, 100, 90},
        {100, 81, 82},
        {83, 65, 85},
        {78, 87, 65},
        {85, 75, 83},
        {91, 94, 100},
        {76, 72, 84},
        {87, 93, 73}};
    GradeBook myGradeBook("CS101 Introduction to C++ Programming", grades);
    myGradeBook.displayMessage();
    myGradeBook.processGrade();
    return 0;
}

This is an example from the book, but it's so weird that an example from book has error. So, I want to ask how to solve this problem.