My school uses class attendance to decide stripes belts (well up to blue belt 4 stripes). 30-35 classes per stripe until you're a blue belt. 72 classes per stripe at blue belt. Personally I don't really like it as a blue belt who struggles with white belts and gets dominated by other blue belts. But I can see how the stripe/attendance system works for a satellite school where there is a purple/brown belt teaching who cannot promote anyone to blue belt. Easier for the head of the affiliate to track who deserves what when its time to come to the school and promote.