Many high schools have test-taking built into the curriculum for the first half of that year of school.
Some states have replaced their standardized testing with the SAT/ACT.
SAT: Colorado, Connecticut, Delaware, DC, Idaho, Illinois, Maine, Michigan, New Hampshire, Ohio, Oklahoma, Rhode Island, South Carolina, Tennessee, West Virginia.
ACT: Alabama, Arkansas, Hawaii, Kentucky, Louisiana, Mississippi, Missouri, Nebraska, Montana, Nevada, North Carolina, North Dakota, Utah, Wisconsin, Wyoming.
Also, the implementation of SAT prep is spotty at best. As with most things, whether the schools have test prep is pretty reliant on how well funded the individual district is. At least that's my experience.