The consequence was studying in order that Spanish could be learned. So each night for the rest of the school year, Bill sat there at the dining table while Darlene got out her Spanish book and did the homework. Bill looked over the book and explained some of the points of foreign language to Darlene. He also made sure that she studied her vocabulary on the nights that no grammar exercises were assigned. Soon the Spanish test turned into B's and A's.
Good grades are the result of hard work.
Obtaining good grades depends on successful completion of homework and learning each and every day. Implement good family discipline. In this approach, your child knows that you mean what you say. What you say is backed up by action. The best action is to insist that the correct thing be done.