Casting Error?? [RESOLVED]

[SaitStudent]

What i am trying to do is load a combo box on a form frmStudents. The way i am going about doing it is my frmstudent on load event has this code

Private stu As Student
    Private Sub frmDisplayStudent_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        stu = New Student
        cboStudents.DataSource = stu.GetStudents
        cboStudents.DisplayMember = "FIRSTNAME"
    End Sub

stu calls to class Student which as a function of GetStudents which does this

Public Function GetStudents() As ArrayList
 
        conn = New SqlConnection(connstring)
        Dim sql As String = "SELECT * FROM Student"
        comm = New SqlCommand(sql, conn)
        Dim stu As New Student
        Dim students As New ArrayList
 
        conn.Open()
        Dim reader As SqlDataReader = comm.ExecuteReader(CommandBehavior.CloseConnection)
 
        Do While reader.Read
            stu = New Student(reader.GetInt32(0), reader.GetString(1), reader.GetString(2), reader.GetString(3), _
                                reader.GetString(4), reader.GetString(5), reader.GetString(6), reader.GetString(7))
            students.Add(stu)
        Loop
        reader.Close()
        conn.Close()
 
        Return students
    End Function

When i try to load the form it says i have a casting error? specifically "Specified cast is not valid."