I need help?

im 14 years old i have 2 sisters one older (shes 15, almost 16) and a younger (11) and my younger sister and i go to a private catholic grade/middle school. my older sister goes to a private catholic high school, where i plan to attend in the fall. my family is barely making ends meet, both my parents work full time jobs. we never go on vacations or shopping sprees or anything extravagant like that. if me or my sisters want something we have to work and pay for it ourselves. when my older sister was in eighth grade the tuition for our schooling was about $5000 a year. now that shes in high school its $9490 just for high school. shes on financial aid, and i dont know how much it takes off. but that is a lot of money thats gone. i am going on field trips for my last week of school and i need money to get food while i'm there but i dont have any. my older sister just says "ask mom and dad they gave it to me theyll give it to you" but she doesnt get how tight money is. shes never home and