The auction sounds like such a winner! I don't know much about school costs, but I'd say just look at your budget. Where is your money going - salaries, supplies, furniture, consumable books, non-consumable books, computers, etc. See what could be adjusted. Perhaps you may need to start charging more for tuition or a smaller discount for church members.
As a former teacher in public school, the fundraiser I loved best was when the principal told us that for $10, we could wear jeans for the whole week. In the whole school year, I think there were probably 5 weeks that she gave us this option. I paid my $10 every time. I'm sure with 80 kids that means you don't have TONS of staff, but if it made them happier to be comfy in jeans as opposed to the normal teacher clothes, then they were happy and you were happy to have made $10. Win-win!
Wish I had more. Halloween is coming up - not sure if you give out candy, but you can always advertise that way - have a brochure or business card tied to a chocolate bar for the parents who come with their kids to your house.
Our volunteer fire dept makes all their money once a year with raffle tickets and a dinner. ($1 a ticket or $5 for 6 tickets. Need NOT be present to win). There's an auction too and it's a lot of fun. Local places donate to the raffle - $50 gift card to Walmart, free oil change from the local Ford dealership, $40 gift card to the local nursery owned by a residen of our community...... We always give $100 and win at least ONE thing!