It is possible to rescue a school, but I think you need to have a group of parents who are specialists at rescuing failing businesses, accountants and lawyers. It's not really the remit of PTA folks, who are happy to fundraise.
If the school has already announced that it is closing, then it may be too late. The vultures from other schools will already be licking their chops.
If there is some hope of keeping the school open, they will need to look at how their debt is structured. They also need to look at how they get their revenue, ie school fees, but particularly looking at their bursary fund. I suspect that they will have an outrageous number of bursaries and relatively low fee income. They need to trim 'back office' to an absolute minimum They need to go after people who owe money.
I don't think the OP needs to panic particularly about finding a new school place. Obviously it depends what your local area is and what is available. Rest-assured, the other independent schools will absorb your pupils and maybe some teachers too.
Start looking for a place and visiting prospective schools. They will probably have special open days for your school's families. Your school may invite other schools to come in with their display stands and flyers. These schools may waive their usual registration fees.
Don't jump ship at Easter as you will be outside of contract and liable for a term's fees. There should be no need to do this, and if the school is definitely closing, everyone will want to have a smooth transition to their new schools.