About 125 students at Macarthur Girls High School in Parramatta will have gone through the school holidays without social media.
The #giveup challenge led by the school's student representative council asked students in years 7 to 12 to give up one or more forms of social media for a maximum of five weeks.
The challenge aims to increase awareness of cyber bullying, and raise funds for ReachOut.com, an online youth mental health service.
Year 10 student Mursal Rahimi chose to give up Tumblr. She said platforms such as Ask.fm that allowed users anonymity were more problematic.
"They basically leave you vulnerable to forms of cyber bullying, and brutal comments that aren't necessary. [They] can have a huge detrimental impact on your mental health," she said.
"The whole point of this challenge is to reflect on the impact it has on our lives, and to think about how to use it so that it benefits everyone and you're creating a positive atmosphere in which everyone can feel comfortable.
"There are some girls at our school that are giving up 12 forms of social media, so I think usage can become obsessive."
Year 9 student Ruponti Atiq has given up use of six accounts: Twitter, Flickr, Instagram, Pinterest, Gmail and Hotmail.
"It's hard at first, but I think it will help us realise how much we actually use social media," she said.
"I stick to my school email now because it's the simplest way of communicating."
Srishti Aggarwal, in year 11, once gave up her mobile phone for the 40-Hour famine two years ago. She said she believed people have become just as dependent on social media.
"It's a luxury," she said. "We don't always need it."