According to a widely cited 2016 report summarized by the Cyberbullying Research Center, about 33.8% of students ages 12–17 reported being cyberbullied at some point in their lifetime.

Because your question asks specifically about students ages 11 to 18 , and the original statistic is reported for 12 to 17 , the most accurate direct figure we have is that roughly one‑third of middle and high school students (around 34%) have experienced cyberbullying at least once.

If you need the exact wording from the most recent Cyberbullying Research Center study or a precise count for 11–18, that may require checking their latest published survey report or data tables, since publicly summarized statistics often group ages slightly differently.