Paris Jackson -- In 'Meltdown Mode' For a Year

Paris Jackson has been in meltdown mode for nearly a year ... this according to sources connected to her exclusive private school.

Our sources from the exclusive Buckley School in the San Fernando Valley tell TMZ ... school officials were aware Paris was dealing with a "major family trauma" when the school year began last September. Based on the timeline, it appears the issue involved Katherine Jackson's mysterious "disappearance" last July.

There were reports Michael Jackson's siblings were holding Katherine as part of a money grab -- something they deny. Paris confronted several of the siblings in a heated argument outside the family's Calabasas home.

Sources connected with Buckley tell TMZ ... when Paris came back to school in September, her grades started dropping and, as one source said, "she stopped caring."

A school official told one of our sources ... what really sent Paris over the edge was when she got an offer to do a movie but certain family members went on an all-out campaign to block it. The source says a school official said, at that point "Paris broke down."

There have been reports Paris was bullied at Buckley and that's what caused her downward spiral. We're told a top school official is adamant ... Paris was NOT bullied and she made the claims to get attention.