Our publications officer does most of our photography (she also handles graphic design and content writing). We also have a second photographer who we utilise on a freelance basis (e.g. after hours events, during peak workload times or when we need to be two places at once!). We are fortunate he is a retired teacher (and used to teach a photography elective!) so he is available at short notice and knows the school and staff well. We find this works well for us and we are able to cover most events!
Once a year we also engage a professional photographer to take our more ‘polished’ marketing images for publications, website, etc.
Hope that helps,