In my opinion too many spanko sites just want to get to the spanking sequences straight away and don't pay enough attention to a realistic build-up - the reason for the punishment, the telling off and so on. A great example of doing this right was the two naughty schoolgirls in the Red Stripe movie, "Demoted to the Fourth". In the first scene the headmistress, Miss Hayworth, gives the two a thorough telling off and carries out an impromptu underwear inspection.
Unsurprisingly, as is the way these days, both girls have very skimpy white knickers under their black tights so Emily and Annabel find themselves demoted to a younger class at the school.
It's a nice extra touch before the punishment really begins (although I must confess that I have a personal preference for the appearance of the the first uniform and the opportunity it offered to demonstrate the disadvantages of their inadequate underwear).