case GRADE_AGGREGATE_MEAN:
case GRADE_AGGREGATE_MEDIAN:
case GRADE_AGGREGATE_WEIGHTED_MEAN:
case GRADE_AGGREGATE_WEIGHTED_MEAN2:
case GRADE_AGGREGATE_EXTRACREDIT_MEAN:
return '<img src="'.$CFG->pixpath.'/i/agg_mean.gif" class="icon itemicon" alt="'.get_string('aggregation', 'grades').'"/>';
case GRADE_AGGREGATE_SUM:
return '<img src="'.$CFG->pixpath.'/i/agg_sum.gif" class="icon itemicon" alt="'.get_string('aggregation', 'grades').'"/>';