Brent Probinsky, the family's lawyer, tells TMZ that the girl's mother calls him twice a day with distress about the school beating that happened on April 13 ... telling him the kid can't sleep, cries constantly and feels generally terrorized by what happened.

As you can imagine, we're told her parents are also overcome with emotion ... especially the mom, whom Probinsky tells us is riddled with guilt from watching it all unfold. We're told the family now has a therapist ... and their first appointment should be this week.

BTW, the attorney shed some light on why the mom just stood by instead of stepping in -- he says she and her husband are undocumented immigrants from Mexico, and she was afraid she'd get deported if she reported it. You can see her hesitation first-hand in new video that we've obtained, showing the principal take an authoritative tone right from the jump.

Luckily, the mom reported it anyway ... and now it's being handled by authorities. Probinsky says the case is being reviewed by the state attorney's office, as well as the school district and the Florida Dept. of Education. Probinsky insists this was aggravated battery -- he's pushing for officials to strip the principal and her clerk of their education licenses ... so they can't teach in Florida ever again.