Crossroads Placement testIf you would like to prepare your child for this tests, I would recommend that you focus on the following concepts:
Concepts addressed on placement test:

Algebra Predictive TestTo prepare your child for the Algebra Predictive test please ensure that they are
1) fluent with their math facts, 2) can graph and interpret graphs, 3) fluent with rational number manipulation (particularly negative integers) 4) able to setup and solve algebraic equations. 
Benchmark tests: These are administered as part of regular instruction (like end of chapter tests).