Often, students who perform poorly on the SAT may perform better on the ACT, and vice versa, though that is not always the case. The ACT’s writing section, for example, is optional; also, the ACT divides the verbal section into two equally-weighted parts, reading (comprehension) and English (grammar and mechanics). It also includes a section on science. Each ACT section is graded up to 36, with the scores being averaged to get the final result (36 is a perfect score).
This more comprehensive approach tends to require better front-end preparation. While there are online practice tests-likewise for the SAT-the best practice tends to be studying up front, sitting the test, deciding whether to study on your own or in a test preparation course, and then sitting the test again. Both the ACT and the SAT, however, include a penalty for wrong answers. This discourages guessing; contrarily, it encourages proper study and preparation. Do not hesitate to prepare the most that you can. Spending the resources to perform well might even qualify you for extra financial aid toward your college degree.