This is the 8686th most frequent Japanese word.
日直
"日直" means "daily duty or class monitor for the day."
In this sentence, 日直 is used to describe the role of a person responsible for daily duties.
昨日は私が日直でした。
Yesterday, I was the day's duty person.
Here, 日直 refers to the daily duties assigned to someone, specifically cleaning duties in this context.
彼女の日直の仕事は教室の掃除でした。
Her day's duty was cleaning the classroom.
This usage indicates that the person assigned as 日直 is responsible for taking attendance.