Students all learn in various ways and no one thing works the same for all of them, but a popular way to learn any skill is with games and interactive videos. There are many resources of this type available online to students, parents and teachers. The sites can vary in their requirement for sign up, registrations and cost, but there are both paid and free options available to learners as well.
Some students do better with old fashion methods which can include flashcards and practice quizzes. If you are a parent of a student needing help with this area of grammar, make sure that the child's feedback is taken into account because they know how they learn best. Some of the games require Flash or Adobe Reader in order to work, so verifying that your system is set up correctly will make grammar practice much easier.
Some sites offer more than one type of lesson, while some offer only one format or another. The sites that require registration often track a student's progress, which can be helpful for a parent because they can see where a student is having issues or how much they are improving. Log-ins and registration are also a good way to make sure students are working on the correct things and not skipping around in lessons.