Here are my comments, but I may have missed (or misunderstood something, so it´s not fail-proof.
    And there are the academical writting, so my opinion may be not so accurate.
    Let´s wait peer-review then.

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...as a monography to my undergraduate major in Nutrition...
 

 ...of low income families... (the kids themselves aren´t in the job market; I suppose...)

...in THE cited shelter/place...or among these students (since you said that they were "escolares, before)

...kids prefference of meals/favorite menu of the target group  etc.... (or other words, but not food preferences of school, school can´t be personified here. It is not a person.)

...the favoured food options in the institution/(instead of shelter, here just for variaty´s sake) OR
their choice of food, mirroring their diet habits at home, that offer extremely low nutritional value...

...Without broadcasting controls, the marketing in the media have an influence of food choices and contribute to a unbalanced diet. Yet, the feasibility of a nutrition education directed at school can encourage the practice of good eating habits.