norton2005, it could just be that you're one of those rare students who actually does what they're told - and lOOks out of the window to assess the correct attitude.
The optical quality of most Spamcans' fly bespattered, oil streaked windscreens is hardly Carl Zeiss! Add to that the bright background (doesn't even need to be sunny - the glare from white clouds is bad enough) and you can soon get sufficient eye strain to give you a thumping headache.
A good set of shades, chosen for reasons other than posing potential, will help considerably. But certainly heed the dehydration, carbon monoxide and headset advice as well!