I got dress coded and givin 3 hours of detention because my bra strap was showing a little in the back ??!?

my hair hid the bra strap .. was not showing or anything and was wearing a tangtop that had straps more than 4 inches wide... and this lady comes and sends me to the dean where i got 3 hours of detention and had to wear an oversized tshirt for the rest of the day .... i go to a public school by the way ....DO YOU THINK THIS WAS FAIR?