I'm happy to say that this practice has changed in the last few years. The prices for tourist attractions are now flat and don't discriminate against internationals. Well, at least in Moscow and St. Petersburg.
Another piece of good news is they are now more laid-back about student admissions. If you have a valid student card, be sure to bring it with you and show it at every ticket booth. They may not take it, or may insist on only accepting ISIC, but that's okay. You can still save a bunch at the major places like the Hermitage and the Kremlin because these two places take all student cards. Mine was from a Canadian university and it opened doors for me!
Judge for yourself:
1. The Hermitage was free! WHAT? I did not see that coming! ($12 savings)
2. In the Kremlin, according to the official website, they only accept ISIC. I still pushed my regular card in the slot and they took it! So I paid only $9 instead of $32. Once in the Kremlin, the Diamond Fund costs extra $15,
but with a student card I got in for $6.
3. At the famous St. Basil's Cathedral as a student you pay $2, as an adult - $8. The difference can buy you a decent lunch.
You are probably thinking "What's the big deal, student discounts exist everywhere?" Not so much in Russia. It is virtually impossible to get anything for free or discounted, especially if you are perceived as a "rich foreigner". It used to be that they would find a ton of excuses to make you pay full price.
Thankfully, not anymore.
Also check out: How To Navigate Moscow Subway