The Group Lists form opens out of the Functions tab on the Finder form. At present it has its own set of criteria independent of the search criteria on Finder. However, the Academic criteria tab on the Finder form does allow you to pick a teaching group and use one of the general lists to display data about the pupils in the group.
In the illustration here, a report is being produced to show the English sets in Year 9. The report has a user defined title. You could also use the Pupil curriculum report to show the subjects studied by each pupil in Year 9 with their teachers or to produce a set of photographs of a particular teaching group - very useful at the beginning of the year! WA Col List provides a list of pupils together with a set of blank columns which might be used for entering marks or attendance. Using the Teachers criterion you could select a list of pupils from a particular year who are taught by a particular teacher.

If you wish to find out how many pupils there are in each teaching group, or in a selection of groups, you should add the Group count report to your list of reports. It must be added here and not to the General list of reports. The name of the report is SubjectCount.