If I understand correctly, this is a very small school, with volunteer teachers?
I’m a former board president of our parish’s Catholic school, albeit a well established one, and have served on multiple task forces to study and reorganize our Catholic schools. I also worked as a development director for a non-profit arts organization for years. It sounds to me as if you need some heavy-duty funding. While raffles and sales are all well and good, and can be a nice addition, that is not enough to provide the kind of income you will need to survive.
To get off the ground, you need to find an “angel”… someone who has considerable funds to donate and who buys into the “mission” of your school. This can be an individual(s) or a foundation with an interest in Catholic education, particularly in establishing Catholic education in your area. Getting publicity about your mission/school is crucial. Start with providing information to your local Catholic paper, and the local secular paper (if there still is one!), as well.
You will have to prove that your idea is viable; donors generally want to fund “winners”. Demonstrate that you are doing a good job educating your students, tout any test scores, etc. Have a definite business plan and vision for your school. The more professional and organized you look, the better the chance of attracting donors.
What sort of support do you have from your diocese and the parish where your school is located? Is there a benefit to them in having your Catholic school succeed? If so, then you may be able to attract funding from either the parish or the diocese.
There are so many variable that dictate how much income you need to be sustainable. Generally salaries and benefits can take up to 80% of your budget. I doubt you will be able to maintain volunteer teachers for long, and you need good teachers in order to succeed.
Prayers and good wishes for your success.