The simple answer to the first question is "no". First, it is a myth that opted-out schools are funded by the Government. In fact, opted-out schools are funded out of the local authority's budget just as they were before they opted out. The Government simply removes from the the local authority the money needed to fund the school and then hands it on to the school in the form of grants.
Moreover, the level of funding for an opted-out school is exactly the same as it would have been if it had stayed under local authority control. These days, with devolved school management, local authorities have clear formulae for providing schools with resources - teachers, money for building repairs, books, equipment and so on - and the opted-out school will continue to be resourced according to the formula operating in its authority for similar schools. If the authority cuts the level of funding to its schools, the opted-out school will experience a comparable cut in funding.
It is true that opted-out schools get some extra money to pay for those services which at present are run centrally - such as personnel, legal support, insurance, psychological services and computer support - but that is because the opted-out school has to buy in such services.
The opted-out school also gets extra money to cover costs which local authority schools do not have - like the need to pay VAT - but in general an opted-out school only gets extra money to cover necessary extra expenditure; it does not get "buckshee" extra money.
Having said that, there are advantages. The budget is protected and if, for example, the opted-out school manages to make some savings, then it keeps that money. That used to be the system for all schools under devolved management but, with the present financial crisis, local authorities are depending on retrieving such savings in order to make their budgets balance.
As for stopping a school closure, this is much less certain. In general, the Government wants rid of half-empty schools and so supports a programme of school rationalisation. Indeed, ministers are on record as saying that they will not allow a school to opt out in order to avoid closure, and they put forward the magic test of "viability" to back up their policy.
However, given that they have decided that Dornoch Academy, a school of some 58 pupils and a per pupil cost of Pounds 6,672, is viable, it is very hard to know how they could judge that a school in Glasgow with, say, some 310 pupils and a per pupil cost of Pounds 4,260 might not be viable.
However, it is not for us to question ministers' reasoning and the likely answer is that, if you are a small inner-city school - you've no chance. If you're a small rural school - then maybe.
However, when considering opting out, the main thing to remember is that it is not a short-term strategy to protect budgets or to avoid school closures: it is for life. Once a ballot has been set in motion, the process cannot be stopped and the board will have to be prepared to take on the running of the school with all the duties and responsibilities of the local authority in terms of providing an "efficient education". The real question is: are you willing to take all that on?