Start your practice in the morning when your mind is fresh and free from any distractions that may arise during the day. Keep track of your practice time in your notebook. Try maintain and extend your practice duration over the course of the week in 5 minute increments. Over time, you will develop greater focus and naturally this will result in longer practice and better results.
Practice requires consistent effort on a daily basis, patience (from both parents and students) and persistence to overcome challenges. Most importantly we need good concentration and attention to detail to be able to quickly identify and fix mistakes. This can be achieved with the right practice set up at home regardless of the duration of practice.