Sure. It's just my district's extended learning program though, I am not in the Boston program.
It was a program that started in elementary school (https://ycsd.yorkcountyschools.org/EXTENDCenter). In second grade they tested us for it, I don't remember a whole lot about it. I do remember it was logic-based and math-based. Every Wednesday from 2nd grade to 5th grade (then in middle school on a different schedule) we would spend in the extended learning program's building (a very small wing). We learned French (though looking back it was more preparing us to learn other languages than actually learning French), did science projects, wrote stuff about a random topic selected out of an encyclopedia, etc. It really is my most fond memory of school and I still keep in contact with the teacher.
Over in the middle school side, we did more advanced topics. We studied the Ebola virus and how it affects the body, we wrote papers about an unknown John Doe in Yorktown in 1770's (then we literally walked to it, separate tangent below), we had a "socratic seminar" where we debated topics, we built a Rube Goldberg machine, all sorts of stuff.
It actually changed my life. Anyone who says advanced education doesn't help simply doesn't see the changes a well-designed, thought out program has. And this was all in a public school. I checked their site recently and they are still running it even through the pandemic, which warms my heart.
I mentioned the one-day, one-time onboarding process. They have since remedied it, instead scheduling tests with students chosen. This is a good solution and I'm glad they implemented it.
Tangent: I lived in Yorktown Virginia, which is probably my second favorite thing about my childhood. The pre-school I went to was a 30 second walk down a hill to Yorktown Beach. In middle school, we read about the Revolutionary War, then took a field trip consisting of walking outside the doors, through the forest and 5 minutes of walking, and just like that we were where it actually took place, with monuments, statues, historical signs, etc.