From TASCtest.com:

The Test Assessing Secondary Completion™ ― the TASC test is designed to assess the high school performance expectations in the Next Generation Science Standards (NGSS). A PDF of the NGSS arranged by Disciplinary Core Idea is available online at:

http://www.nextgenscience.org/next-generation-science-standards 

The NGSS performance expectations state what all learners should be able to do in order to demonstrate their understanding of science. Each NGSS performance expectation integrates a Science and Engineering Practice, one or more Disciplinary Core Ideas, and a Crosscutting Concept. Each NGSS performance expectation also includes a Clarification Statement and an Assessment Boundary to provide further information for the purposes of curriculum, instruction, and assessment. 

The TASC test Science assessment will include items for the disciplines of Physical Sciences, Life Sciences, and Earth and Space Sciences. Each discipline is subdivided into several Core Ideas, which each contain multiple performance expectations. Each test item assesses one performance expectation. Items may require recalling knowledge, applying knowledge and skills, or reasoning. 

The number of test items per Core Idea is proportional to the number of performance expectations within the Core Idea. As a result, each Core Idea will have about 2-5 items on a given test. A given test will not necessarily include items for every performance expectation present in the NGSS, though any performance expectation is potentially assessable.