attendance

my attendance for year 11 autumn term was 94.4%, which, according to google, is good but could be better, however i fear my attendance might drop a lot due to me been absent the entire first week back after Christmas because of a holiday (that i tried to tell my parents that it would interfere with school, but the tickets were REALLY expensive and the booked months before so it was too late to cancel), not to mention i had instances where the school would mark me absent because i was at prefect meetings so my mum has to email them to correct it (wether they do is debatable) and now i’ve fallen ill and really don’t want to go to school tomorrow since i have an english test, but i dont want my already low attendance for this spring term to get lower. how do they even calculate overall attendance? by taking each attendance over each term and get the average? either way what should i do??