My younger two took a mock test under “test” conditions sophomore year without prep.
Both had Algebra II as freshman and precalc as sophomores. They scored around 25-27.
Private tutor 1x per week for 6-8 weeks and test in June of Sophomore year. Scored 29 and 30. 29 said he struggled with timing.
Retook without prep sometime Junior year. 29 increased to 35, 30 increased to 33.