This year we have used varied ways of practicing grammar and language mechanics. Here are a few links I think you may find helpful and could just be fun for your child!
www.quia.com is a wonderful site. Just ask for the 30 day free trial. There are many subjects to choose from to study.
www.kent.k12.wa.us/curriculum.writing/elem_writing/Bib is another site with several activities.
Also, www.internet4classrooms.com/skills_4th_original is another site to try.
Reviewing nightly the work we've done in class will also be helpful. Encourage your child to double check their work and not to rush.
