absenteeism actually is the word you're looking for.
: the act of staying away from work without a good reason.
: the act of staying away from work without permission or prior notice.
Alternately, you might consider
: to fail to attend purposely: cut a class.
cut class and cut school
: to skip a school class or a day of school without an excuse. As a joke, one day all the students cut their math class and went to lunch. Jane was grounded after she cut school last Friday.
(McGraw-Hill Dictionary of American Idioms and Phrasal Verbs)
: to fail to attend or participate in skip the tournament
Half of MPS students regularly skip school, report shows
: Slang to skip (class or school)
tv. & in. to skip or evade someone or something. Pete ditched class today.
(McGraw-Hill's Dictionary of American Slang and Colloquial Expressions)
Truancy can be described as any unauthorized absence from school, cutting school, skipping school, ditching school, etc.
Red Bluff Police Department
Even the President is ditching work to see Star Wars