Many San Francisco high school students could be in for some tense family discussions around the dinner table this holiday season.

The public school district is mailing notices to just under half  the class of 2014, or 1,900 students, telling them they've fallen behind and may not graduate unless they catch up.

If it sounds like an unusually large number of students in jeopardy -- it is.

San Francisco Chronicle reporter Jill Tucker spoke with KQED's Stephanie Martin to find out why.