Schools and churches serve the needs of the same local community. Consequently, for them to make strong links and work together in partnership can only result in better community relationships which will help develop community cohesion. This will be really positive for pupils.
Getting involved will take time and effort and must result in reliable and trustworthy support for the school.
Remember that any church members going into a school to help will need to be CRB checked. If that has been done for church activities, that may suffice. Consult with the headteacher for the correct procedures.