How to pass dynamic arrays in FreePascal correctly - parameter-passing

Question

In this FreePascal code I write, I found that in a dynamic array of length 'n', it always contained a random value in element 'n'.
I understand why that is, however, I am wondering if perhaps there is a flaw in the way i've written my code. I've pasted it below. I'd welcome any corrections.
program LinearSearch;
{$mode objfpc}{$H+}
uses
{$IFDEF UNIX}{$IFDEF UseCThreads}
cthreads,
{$ENDIF}{$ENDIF}
Classes, SysUtils
{ you can add units after this };
{$R *.res}
type
ArrayOfByte = array of Byte;
Function findMaximum(studentMarks : ArrayOfByte; numberOfStudents : integer)
: integer;
var
maximumMark : Integer;
studentWithMaximumMark : Integer;
index : integer;
begin
setLength(studentMarks, numberOfStudents);
maximumMark := studentMarks[0];
for index:=0 to numberOfStudents do
begin
write(IntToStr(studentMarks[index]));
if index = numberOfStudents then writeln('.')
else write(',');
end;
for index:= 0 to (numberOfStudents - 1) do
begin
if studentMarks[index] > maximumMark then
begin
maximumMark := studentMarks[index];
studentWithMaximumMark := index;
end;
end;
write('Maximum score of ',IntToStr(maximumMark),' was achieved by ');
Result := studentWithMaximumMark+1;
end;
var
studentMarks : ArrayOfByte;
numberOfStudents : Integer;
studentWithMaximumMarks : Integer;
counter : integer;
begin
write('Enter the number of students: ' );
readln(numberOfStudents);
setLength(studentMarks,numberOfStudents);
writeln('Input the grades for the following students:');
for counter := 0 to (numberOfStudents - 1) do
begin
write('Student ',counter+1,': ');
readln(studentMarks[counter]);
end;
writeln('Data has been input. Finding student with maximum marks.');
studentWithMaximumMarks := findMaximum(studentMarks,numberOfStudents);
write('student no. ',IntToStr(studentWithMaximumMarks));
writeln;
writeln('Press ANY key to continue');
readln;
end.

Answer 1

In Free Pascal dynamic arrays are zero based. So the first element is MyArray[0] and last element is MyArray[High(MyArray)] which is equal to MyArray[Length(MyArray) - 1]. You should never access MyArray[Length(MyArray)].

Answer 2

...I found that in a dynamic array of length 'n', it always contained a random value in element 'n'. this is because you are accessing a value beyond of the bounds of the array, check in the procedure findMaximum the line
for index:=0 to numberOfStudents do
must be
for index:=0 to numberOfStudents-1 do
Also you can remove the first line of the same procedure setLength(studentMarks, numberOfStudents);