But if your school is in an expanding area such as Berkshire or Hampshire or is popular with parents you may find yourself having to hire a temporary classroom for the coming school year.
It is a decision you will have to make quickly. Any delays in getting the paperwork sorted out could mean that in September you will find yourself with a class, a teacher and nowhere to put them.
Before your council contracted out its professional services and before you had a substantial delegated budget at your fingertips, you would have left it for your local education authority to sort out. In most cases this is still an option, but one that is looking increasingly expensive. Many heads are beginning to suspect that they can get a better deal outside from the army of building professionals and contractors waiting on the sidelines.
Nearly all manufacturers of prefabricated (they prefer to call them modular) classrooms will hire as well as sell and will be pleased to point out the differences and come up with a solution that will suit a school's needs. If you are still contractually tied to the local authority, the choices are limited. The standard pattern of procurement is that county councils buy in temporary classrooms direct from the manufacturer. Dave Sparrow, principal officer for West Sussex County Council's property department says: "We service all the other council departments, but classrooms make up 70 per cent of the modular buildings we buy."
Like most councils, West Sussex operates a system of term contracts. Manufacturers bid in competition for an exclusive contract to supply all the county's modular buildings, usually over a two-year period. The contract is open-ended, there is no guaranteed minimum order and no maximum. Last year the manufacturer Rollalong supplied West Sussex with 20 modular units at prices ranging from Pounds 20,000 to Pounds 200,000.
Modular buildings, ideal for rapid assembly, can have a design life of up to 40 years. Some manufacturers claim longer. They are factory made and most are bespoke, designed for a specific school and a specific purpose such as an eight-classroom science block or a nursery unit. LEAs are keen to offer schools modular buildings as a once-and-for-all solution to accommodating increased pupil numbers. If the school roll falls, then the council has the option of dismantling the building and transferring it to another school.
The upside of leaving it to the county is that the property services department takes care of planning and building regulations, potential headaches for schools wanting to arrange their own temporary classroom provision.
But heads can have good reasons for choosing to spend their own money on classroom hire. They may prefer a traditionally built extension or they create more space within the existing buildings by internal refurbishment. Hiring a classroom can provide a breathing space in which to consider all the options.
When the independent Vine Hall School in Burgess Hill, Sussex wanted to open its doors to under-fives, the school decided to hire in the extra classroom space. Rovacabin supplied it with two classrooms and a toilet unit on a year's hire. Rovacabin's managing director, Brian Woodham, says: "They're hedging their bets. They paid for the accommodation out of the year's revenue rather than commit themselves to a huge building programme which may not be needed. "
The economics of hire is a fine balancing act. Added to the cost of hire is the cost of installation, connecting the classroom up to mains services and building a pathway and steps up to it. Then there is the cost of dismantling and removal. Under a year, hire is rarely cost-effective. And if the hire is for several years it can make more sense for the school to buy a modular building outright, price being dependent on quality. Mr Sparrow says: "Three years is the break-even point. After you've had it any longer than that you would be spending on hire more than the building costs to buy."
But over the past few years hire rates have dropped as competition among manufacturers for a slice of the lucrative and steady schools market has increased. The recession, which hit the construction industry hard, persuaded a lot of firms to switch production from site huts to classrooms. Some companies entered the schools market for the first time.
Mike Gardener, marketing director of Elliott Medway, says: "Over the past five years we've faced competition from system builders. Increased competition and price cutting have gone hand in hand."
Manufacturers are now marketing their products and services aggressively. Rovacabin's Mr Woodham says: "We've been marketing directly to schools with mailshots and advertising. Three years ago the number of modular classrooms we hired was negligible. Now, it's 10 per cent of our hire fleet."
So, what level of service can you expect from a hirer? The biggest single worry for heads is that the temporary classroom will not be in place for the start of the autumn term. When councils are looking after things, most have a get-out clause in their term contracts which allows them to sack the modular building firm if it fails to meet performance criteria.
But outside hirers are keen to provide as good a service as they can and keep their school client informed about what is going on. Elliot Medway, for example, offers schools a planning service to advise on building regulations and planning permission and a host of other building matters. Mike Gardener says: "We now offer a complete one-stop shop package including survey, full design and project management - a complete turnkey service." Rovacabin's Brian Woodham claims guaranteed delivery times of four to six weeks for hired classrooms and a week to 10 days for installation.
The modular building industry is geared to short lead times but it still needs the co-operation of schools to offer them the best possible service. Between the start of the schools' financial year and the assessing of pupil numbers there is not much time for heads to find hire companies, compare quotes and start planning.
Graham Cox, marketing director of Elliot Workspace, says: "The problem is everyone we employ wants to take their holidays over the summer. If schools had more foresight they would pre-plan at an earlier stage and order in April or May."
Orders placed in June or even July put a tremendous strain on the hire companies to sort things out and deliver over the schools' holidays. If you have left it to the last minute, you have probably only yourself to blame if things do not work out.