Children from the upper classes have access to better health care, which includes tools such as orthotic shoes, orthodontic treatments and support for a variety of other irregularities often not covered by insurance. Lower class families go without.
Many in the upper classes work with trainers and coaches to develop personal gym and yoga routines. This all takes time and money, neither of which are abundant for those in the working class.
As adults, plastic surgery and botox treatments are beyond what most working class people can afford. Access to a healthy diet and lifestyle can also be a challenge. All of these physical advantages have a noticeable cumulative effect.