As mentioned it is pretty easy to review IGC files and see what one is actually doing. I agree telling students to use about 45 degrees is good as that is what they will percieve it at. I am one that if asked would have said I was probably between 30 and 45 degrees abeam my touch down point. Seeyou says different here are the number for 7 of me recent flights.

Altitude(ft) Distance (ft) Angle(deg)
870 2904 16.7
1053 2270 24.9
1699 3326 27.1
1751 4540 21.1
823 1900 23.4
1072 3500 17.0
951 3273 16.2

average 20.9
minimum 16.2
maximum 27.1