I use this at each lesson. The student is awarded a music note (quaver, crotchet, minim, semibreve, breve) according to how well I think the student has attempted or mastered the goal. These music notes are added as 'beats' & used as currency in the Piano Shop (a suitcase of treats that are 'bought' with 'beats') & expressed under 'Total' as a simple musical algebra result.
This is Version 4 & this year I plan on giving a crotchet rest for areas that the student hasn't attempted. The crotchet rest will have a negative value of -1 beat on their cumulative total.