The retailer is uploading the three TV ads on its Facebook, Twitter and YouTube channels today, alongside an exclusive online video called "both getting picked."
The three 20-second TV ads called "growth spurt", "getting dressed by yourself" and "finding your own style", will air for two weeks in Scotland and Northern Ireland from tomorrow and in England and Wales from 14 August. They were created by Rainey Kelly Campbell Roalfe/Y&R.
Each ad was street cast and features children at different stages of their school life giving unscripted views on M&S’s schoolwear.
The TV ads will be supported by a digital and social campaign that will use the #everymilestone hashtag.
The campaign focuses on the memorable milestones in a child’s school life and aims to showcase the innovations in M&S schoolwear, which make getting dressed easier for children and the clothes last longer.
Patrick Bousquet-Chavanne, the M&S executive director of marketing and international, said: "As we return to television this back to school period, we wanted to create an inspiring campaign that uses warmth, spontaneity, fun and emotion to tell stories about our unique schoolwear innovations, which help enhance our customers’ lives every day.
"Schoolwear is also one of our most popular online purchases – so there’s a strong digital and social element – ensuring that we engage with parents in the place they are most active."
The work was created by the art director Nicola Wood, the copywriter was Andy Forrest and it was overseen by the creative director and RKCR/Y&R chairman, Mark Roalfe. The films were directed by Si & Ad through Academy.
Earlier this month, M&S reported its 12th consecutive drop in quarterly sales of general merchandise, with trading hit by problems at its website. Mark Bolland, the chief executive at M&S, said the retailer's sales performance in clothing and homewares was "not good enough".