Unlike schools we do not have fixed supervisory ratios, partly because some of our students are over 18 and legally adults. Our ratios are determined by the level of risk as assessed by trip leaders; while two staff might accompany a coach trip to a theatre we might have a 6:1 ratio for a group going up a mountain.
If staff are driving minibuses there will be a higher staff to student ratio than if the group is travelling by public transport or by coach. When trips involve hazardous activities (e.g. climbing or kayaking) we use our own qualified staff or hire in additional instructors.
If a large group will split into several smaller groups to visit various locations (e.g. London museums and art galleries) we would expect a member of staff to accompany each group.
Should a student health issue or additional support need be involved, additional staff could be assigned if necessary.