select schoolId, avgClassSize, totalStudents from (
     select schoolId, avg(classSize) as avgClassSize, sum(classSize) as totalStudents
     from classrooms where stateCode in ('CA", "NV') group by schoolId
) as agg
where agg.avgClassSize > 30 order by agg.totalStudents desc;

Classrooms{
  String stateCode;
  int schoolId;
  int classSize;
}

public List<SchoolReport> getSchoolReport(Session session, List<String> states) {
        // The inner query
        DetachedCriteria agg = DetachedCriteria.forClass(Classrooms.class);
       
        // list the aggregation fields
        ProjectionList projections = Projections.projectionList();
        projections.add(Projections.groupProperty("schoolId").as("schoolId"));
        projections.add(Projections.avg("classSize").as("avgClassSize"));
        projections.add(Projections.sum("classSize").as("totalStudents"));
        agg.setProjection(projections);

        // restrict inner query to only desired states
        agg.add(Restrictions.in("stateCode", states));

       
        // The outter query
        DetachedCriteria outter = DetachedCriteria.forClass(SchoolReport.class);

        // Somehow reference the inner query
  //??????????????????????????????
        outter.add(MAGIC_HERE(agg));
  //??????????????????????????????

        // restrict the report to schools which have large class sizes
        outter.add(Restrictions.gt("avgClassSize", 30));

        // Show largest schools first
        outter.addOrder(Order.desc("totalStudents"));

        // do actual query
        return (List<SchoolReport>)outter.getExecutableCriteria(session).list();
}

public static class SchoolReport{
  int schoolId;
  int totalStudents;
  double avgClassSize;
}