Both sides are spinning the story, but it does seem like the EFF is fighting the good fight here:
"The computer in question also had encrypted 2014 FCAT questions stored on it"
Of course, this is not relevant as the files were not tampered with (also mentioned in the article), however it trumps up the perceived seriousness of the so-called "cybercrime". It's link-bait from the Sherrif's department.
"Green had previously received a three-day suspension for accessing the system inappropriately."
More link bait as other students got in trouble as well. The students frequently used the same administrative account to screen-share with their friends. More alarming is that the school didn't do anything about this the first time around. Eg. move the encrypted files to a different account / network, or lock things down. But again, this had nothing to do with encrypted files.
"Green was released on Wednesday from Land O'Lakes Detention Center into the custody of his mother. He'll likely be granted pretrial intervention by a judge, sheriff's detective Anthony Bossone said."
So they don't have a case (changing a desktop background is not gonna fly as a cybercrime with a jury, no matter how many times you do it), or have decided that they've wasted enough taxpayer dollars trying to scare future "hackers" straight. It's ridiculous we're even talking about this - that it got this far.
The teens mother probably offers the most level heaved observation of the situation:
"The teen's mother, Eileen Foster, said she understands her son did something wrong, but doesn't think he needed to be arrested. Also, she said, it shouldn't have been so easy for students to access the system."