This is the 15900th most frequent Russian word.
пропущены
"Missed" or "omitted."
Here, 'пропущены' is used in the context of something being omitted or left out.
На бумаге были пропущены важные детали.
Important details were omitted on the paper.
In this sentence, 'пропущены' implies that the lessons were skipped or not attended because of illness.
Пропущены уроки из-за болезни.
Lessons were missed due to illness.
'Пропущены' here denotes the absence of certain words, indicating they need to be added.