Comparing scores between students at different HSs is an easy way to normalize different HSs, but I wouldn’t say it’s the “best way”. Nearly every study that controls for a measure of HS GPA and a measure of HS course rigor finds that SAT I scores add little value in predicting academic success in college beyond what is available in the rest of the application. I can link to some, if there is interest. Tests that are more focused on specific courses, such as AP, tend to be more helpful in predicting academic success (but not as helpful as transcript). However, they have their own set of problems. If you weight AP scores heavily, then you can be putting students who attend HSs that offer no/few AP classes at a disadvantage.
In my opinion the “best way” would be to use a variety of sources beyond just scores. For example, FERPA has shown that some elite colleges rate LORs on a scale of 1 to X, giving a LOR score that can be compared across students at different HSs. You can also compare essays, ECs, awards, and a variety of other factors in addition to tests. The combination is far better than any 1 source alone.