The academics insisted that the garment was encouraging kids to defy bans on MP3s in class.
The jackets made by M and S have "a strategically placed iPod pocket which doesn't bulge" plus an "iPod connector with a hidden circuit".
The students use a keypad behind the lapel to control their music gizmos. The blazer also features "lapel loops concealing the earphone wires".
"Providing pockets in school uniforms to conceal these items tantamounts to legitimizing the flouting of school rules," The Sun quoted Chris Keates, of NASUWT, as saying.
Defending its stand M and S said that "Blazer for iPod" was meant for use traveling to and from school.