ELA MCAS Practice Tests (with the TestNav app). You can also find answer keys here to check your work.
http://mcas.pearsonsupport.com/tutorial/
http://mcas.pearsonsupport.com/student/practice-tests-ela/
The links below will take you directly to two different practice tests on the computer. The first one is a 4th grade practice, and the second one is a 5th grade practice. Both assessments have value in getting familiar with the kinds of questions you'll see on the real test in April.
Grade 4
https://ma.testnav.com/client/index.html#login?username=LGN334614605&password=NX6VGLT4
Grade 5
ma.testnav.com/client/index.html#login?username=LGN553063407&password=ZSQGF646