Different types of school are funded in different ways. Some newer types of school, like academies, are funded directly from central government. Most other school budgets are agreed by Local Authorities who get the funds from central government. The amount of money they get depends on a locally agreed formula relating to the number and age of the pupils in the school. Some additional funding for specific initiatives may come direct to schools from central government. It is generally agreed that there is more money being allocated to education now than ever before.
Despite that, many schools struggle to provide the education they would want to give, and so continually fundraise for the additional resources they need. This can be done in a variety of ways. Often the PTA or Friends Association will hold events... school fairs, quiz nights for example. There will be lots of opportunities for church members who belong to school groups as parents to get involved with the fundraising activities. Churches sometimes join in directly by putting together a quiz team or offering to 'man' a stand at the fair.
In addition, there are many opportunities to collect vouchers for schools from well-known supermarkets or cereal box tops. If this is publicised in the church, with encouragement for the congregation to collect them, it can make a big difference to the amount of vouchers collected, particularly in a small school. Make sure someone is responsible for taking them to the school well before the deadline for redemption!
Churches sometimes have access to trust funds which make grants to schools. Advice to headteachers about such funds will always be welcomed.