Well, it's taught up until grade 11, because the vast majority of students cannot learn to write without major mistakes up until grade 11 of 3-4 days a week of 40 min Russian classes. This is purely Russian spelling - not Russian literature. Russian literature is a separate class.

  To put it in perspective, that is the same amount of time you spend learning math and 2x more than you spend learning history, geography, physics, etc.

In fact, in the school where I went to where English is taught as a second language, after 7 years, English becomes English Literature. So I learned to write English without mistakes before learning to write Russian without mistakes being a native Russian speaker, regularly writing in Russian and never interacting with native English speakers.

Sounding out words is not the issue. The issue is writing correctly in ambiguous cases.

Here is a good example:

http://videotutor-rusyaz.ru/uchenikam/teoriya/144-pravopisan...

This deals with whether you put one letter н or two in adjectives suffixes. Basically it depends on a lot of factors and there are many exceptions. There are also other suffixes each of which has specific rules based on a number of factors such as what the root of the word is, how it is formed, and the meaning of the word.

This one single issue is already more complex than anything in English.

There are a ton of other suffix and word conjugation issues you have to worry about.

The only rule in English that I can think of where you have to interpret a sentence in your head before saying it is "I" vs "me".

Example:

He told Tom and me to get ready.

vs

If John and I get married, we’ll have two kids.