The word average student is vague. The examiner checking your answer sheets has no idea whether you are an average student or a topper. So it all depends on your preparation for the exam. You can get above-average marks if you study well and attempt the exam well. Similarly, not studying well might result in below-average marks.
The rough estimate of average IGNOU marks is around 55-60 marks (out of 100).
So it can be said that an average student can score first division easily. It mostly depends on how you write your answers.