My solution would be to have a new column, which is weeknumber - this
could either use the weeknum function or could take us back to the
Sunday (for example) - the Sunday version would be

=AttendanceDay-day(AttendanceDay)

(replace AttendanceDay with the cell reference)

This gives you a column where all days in a given week are on the same
date, then you can use a pivot table to get your data out.