(MCT) — ST. LOUIS — A sexually inappropriate tweet about a teacher started it, but by the time administrators at Granite City High in Illinois scoured the recent social media activity of students, at least 10 were suspended, unleashing an explosion of criticism online.

School administrators said they had no choice but to act because students violated school rules. But an official with the Illinois chapter of the American Civil Liberties Union said the school district and others throughout the country are commonly going too far when it comes to monitoring Internet activity outside of school.