Usually when you hear about a settlement (and not a plea deal) that means this was a civil case and not a criminal one. A civil case doesn’t weigh in on whether or not criminal charges will be brought.
If enough people push the Attorney General of that state to pursue charges they still could (Edit: it’s been 14 years and the Statute of Limitations is 5 years for wiretapping which I think is the highest possible charge). But there is a higher standard for evidence in criminal trials. Not to mention the defense’s argument would likely be that schools have the right to wiretap students’ issued laptops, so the AG probably doesn’t want this to go to court and end up enshrining such a right when it currently holds civil liability due to the civil case succeeding.