SAT tests math, reading and writing. The test is scored on a range from 400-1600. Colleges have various score requirements for entrance. The SAT costs $55 (students on free/reduced lunch test for free). GPISD covers the SAT test for all Juniors. Students can register for the SAT online at College Board.
ACT tests math, reading, science and English. The test is scores on a range from 1-36. Colleges have various score requirements for entrance. The ACT costs $63. GPISD covers the cost of testing during your Junior year. Students can register for the ACT online at act.org.
The TSI test is required to enroll at any college. The scores are not used to admit students only to assist students in taking classes. The test determines if students are college ready in math and English. Students must score a 950 on Math or between a 910-949 with a diagnostic of 6 in math. For English, students must score a 945 with an essay of 5-8 or a score of 910 with a diagnostic of 5-6 and an essay of 5-8. The TSI is given at GPHS (check the testing calendar).
The Khan Academy has numerous resources to study for these tests. You can also find numerous resources at the individual websites for the test.
College Board for SAT
ACT for ACT
Accuplacer for TSI