It usually takes 3 years to get through law school. That seems to be the baseline. The American Bar Association only accredits schools that provide 3 years' worth of courses for a law degree.
Not all students graduate in 3 years though. If they chose a reduced schedule or a part-time option, this would delay their graduation time; rather than 3 years, it could take 4 or more years to finish their legal education.
Alternatively, some students may take summer classes or serve an externship in a related role, enabling them to obtain credit and complete their schooling in less than 3 years.