In Miami-Dade, high school students cannot use their phones during class periods, but can use them during lunch and other breaks. Our survey shows 90% of teachers support banning cellphones in younger grades, as the new law mandates. Social media? Ever since Broward instituted its near-total cellphone ban last year, high school teachers have noticed the biggest impacts. As an example of the pernicious impact social media has on mental health, Van Buren told us even the most popular kids are telling her they constantly judge themselves against the impossible standards they see on social media, and that negatively impacts their self-esteem.