Yes. There is no comparably rigorous platform of mathematics education anywhere in the West, and the best comparison in the East is India.
By the time a student at a good Russian school finishes 11th year, he or she would have had 12 years of mathematics (starting year 0)—7 of which are advanced—4 years of informatics (algorithmics and computing), along with highly mathematical classes such as physics (for 6 years), biology (for 6 years, 4 with mathematics), chemistry (6 years), electronics (5 years) and electives.
In addition, a student living in a major city can join numerous FREE (or cheap) government-sponsored programs on weekends. For example, in Moscow near Kropotkinskaya, there is a mathematics “camp” run all school year for mathematically inclined students, taught by faculty from Moscow State and other renowned schools. (Many of the problem sets I’ve seen them hand out to 12 year olds there I couldn’t solve if they were multiple choice!)
Even outside the big centres, there are numerous such programs and camps (legitimate ones) that are free or cheap and of exceptional quality.
Moreover, I am not alone in my opinion. Programs like—in which students from MIT, Princeton, Harvard and the like compete to spend a semester studying mathematics in Russia—attest to how mathematics students from top US and Canadian schools view Russian math education. Nonetheless, even without that endorsement, , one of the sponsors and a university which draws almost solely from Russian schools, has some of the most renowned mathematicians on its faculty and alumni.
Yes, school quality varies across neighbourhoods, cities and regions. But this is the case in every country on earth, including India. Moreover, this was true during Soviet times as well, when students from regions and distant Bloc countries had little chance of gaining entrance to the best classes—often because they lacked connections. Today this is actually improved.
And yes, in the 90s and early 2000s corruption took a toll on Russian schools, as rich parents with stupid children paid bribes to get them into coveted schools and universities, pass exams, internships and jobs. But rich Russians also did this all over Europe—even at universities. And the Soviets were often not clean either (with the recent question about many degrees and dissertations), so I am not sure why some Quorans here have suggested the Soviet days were much better.
In any case, the deterioration and corruption is being actively (and even aggressively) address, and the schools of 2018 are not the schools of 2007. Teachers’s compensation packages have been boosted, for one thing, and anti-corruption measures that put them on the spot and carry serious penalties are another. Older teachers (many of whom took part in the strange practices of the 90s) are being replaced with younger counterparts and oftentimes today’s teachers are dismissed for offering “tutoring”.
I would still put Russia’s high school math, science (art and music) graduates up against any in the world, and I suspect they would prevail against most.