Below is a website that you can use to practice for both the reading and math MCA tests. Once you get to the site you will need to put in the learner locator number of the topic you want to practice.
3rd grade assignment numbers are listed here:
mathematical reasoning: as113363
number sense: as113371
patterns, functions, and algebra: as113372
data analysis: as113373
spacial sense: as113374
vocabulary expansion: as112659