Have to disagree here. It's much better than the 3 county high schools. Nowhere near the problems of the others and students actually learn something.
I'd be curious of some numeric proof for your statement. Comparing children of both schools (private and public) of the same socioeconomic backgrounds, you'll probably find the public schools do better. I ran for board of ed in St. Mary's and used to have this data. Also, the public schools have more programs for the motivated.
www.niche.com has some data, but you need more data than is presented to make determination. SMCPS average SAT 1180. St. Mary's Ryken, average SAT 1190. Given Ryken probably doesn't have lower socioeconomic students, I think this data alone would show SPCPS may be better. SMCPS also used to pay for many to take the SAT, when many students had no aspiration for college.
Also note, public schools don't have to hire certified teachers. I was unimpressed with several in Ryken. Some, were also very good.