Harcourt School has developed online software for grades 2-5 that provides proofreading exercises. Simply select a grade level, type your name in the space provided, and the computer will provide you with grade-appropriate questions on grammar, spelling and usage. Proofread the sentence correctly, make your changes, and push enter. If you enter the wrong answer, the system will give you a hint or the correct answer.
The University of Missouri has devised a series of games that deal with late elementary- junior high grade level grammar. You can even choose what specific area you want to work on whether it be commas, punctuation or grammar.
Get a professional grammar check online at grammarly.com. The site will give you a free report on your skill level, which will provide an assessment of the things you need to work on.
Visit several websites and analyze them as if you were a professional copy editor. Write down any errors, and, next to the errors, write the correct sentence or spelling.