半夜在校长楼下唱忐忑深夜在主任家里跳芭蕾
[bàn yè zài xiào zhăng lóu xià chàng tăn tè shēn yè zài zhŭ rèn jiā lĭ tiào bā lĕi]
Literally means 'Singing Anxiety under the Principal's Building at Midnight, Dancing Ballet in the Dean’s House at Night.' It describes someone doing exaggerated, unconventional things in inappropriate places or times, often indicating rebellion or mischief.