I give my Thursday evening group a list if ten irregular verbs to learn every week. The following week we do a test and they get ten more plus any errors. Three out of the four learn their verbs, the forth, no, so next week they've got sixteen. The boy who doesn't bother is really good in class but does nothing at all during the week. It's spoiling the ambiance a bit. These kids parent's are paying for extra lessons on top of their normal workload. I try to make things as interesting as possible for them. Sorry to moan, think I'll have to contact the parents.