编译时有错误，我该怎么改



unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    ListBox1: TListBox;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation
type
Thuman =class
private
name:string;

public
procedure Draw;
procedure SetName(c:String);

function GetName:String;

end;
procedure Thuman.Draw;
begin
Form1.ListBox1.Items.Add('师生信息');
end;
procedure Thuman.SetName(c:String);
begin
name:=c;
end;
function Thuman.GetName:string;
begin
result:=name;
end;

type
Tstudent=class(Thuman)
private
age:integer;
school:string;
public
procedure Draw;
end;
procedure  Tstudent.Draw;
var
mystr:String;
school:string;
begin
mystr:='学生姓名是'+name+',年龄为'+IntToStr(age)+'，学校为'
+school;
Form1.ListBox1.Items.Add(mystr);
end;

type
Tteacher=class(Thuman)
private
age:integer;
gz:integer;
public
procedure Draw;
end;
procedure  Tteacher.Draw;
var
mystr:String;
begin
mystr:='教师姓名是'+name+',年龄为'+IntToStr(age)+'，月工资为'
+IntToStr(gz);
Form1.ListBox1.Items.Add(mystr);
end;
{$R *.dfm}
procedure TForm1.Button1Click(Sender: TObject);
var
s1:Tstudent;
t2:Tteacher;
begin
s1:=Tstudent.Create;
t2:=Tteacher.Create;
s1.age:=20;
s1.SetName('victor');
s1:=Tstudent.school('changjiang');
Form1.ListBox1.Items.Add('学生信息如下：');
//Form1.ListBox1.Items.Add('学生信息如下：');+s1.GetName+s1.School+IntToStr(s1.age));
s1.Draw;
t2.SetName('xiao hong');
t2.age:=30;
t2.gz:=1500;
Form1.ListBox1.Items.Add('教师信息如下：');
t2.Draw;
s1.Destroy;
t2.Destroy;
end;

end.

1)、Tstudent.Draw 过程里面不需要再定义变量school,直接屏蔽掉;即
procedure  Tstudent.Draw;
var
mystr:String;
//school:string;
begin
mystr:='学生姓名是'+name+',年龄为'+IntToStr(age)+'，学校为'
+school;
Form1.ListBox1.Items.Add(mystr);
end;

2)、procedure TForm1.btn1Click(Sender: TObject)过程改为：
procedure TForm1.btn1Click(Sender: TObject);
var
  s1:Tstudent;
  t2:Tteacher;
begin
  s1:=Tstudent.Create;
  t2:=Tteacher.Create;
  s1.age:=20;
  s1.SetName('victor');
  //s1:=Tstudent.school('changjiang');
  s1.school := 'changjiang';
  Form1.ListBox1.Items.Add('学生信息如下：');
  //Form1.ListBox1.Items.Add('学生信息如下：');+s1.GetName+s1.School+IntToStr(s1.age));
  s1.Draw;
  t2.SetName('xiao hong');
  t2.age:=30;
  t2.gz:=1500;
  Form1.ListBox1.Items.Add('教师信息如下：');
  t2.Draw;
  s1.Destroy;
  t2.Destroy;
end;