Although many Russians believe that they have the best school education in the world, the reality is different.
There are very many bad teachers and bad schools in Russia and were at the time of the USSR.
This is especially concerning discipline. The teachers cannot use physical force to bring the pupils to discipline,
and no working mechanism exists.

In the Soviet times the parents were responsible for their children, so a parent was obliged to bring his child into the lines with the discipline.
Otherwise the school could write to his employer and the employer had to take measures against the parent (stripping of financial bonuses
for example or slowing down the carrier progression). This was not always effective because there were parents who were criminals,
alcoholics and who did not bother about their carrier.

Now this mechanism does not work at all because many parents are employed at private enterprises which are not obliged
to take any measures or somehow react to the school's letters.

There are no other mechanisms: for example the police cannot do anything about people who did not reach 14 years and even elder persons can be prosecuted
in only serious cases. The school marks as a rule have no impact on further carrier.

A bad-behaving student should be theoretically forced to repeat a year in the same class, but this is usually not done because the teachers and the administration usually
want to get rid of bad pupils rather than keep them in school for a longer time. Also an elder and stronger hooligan among younger pupils would be even more trouble for a teacher.

That said, the most schools in the USSR were standardized and employed the same curriculum and teaching plan with small variations for some specialized schools inclined in favor of some subjects.

The curriculum was (and is) quite intense. I studied mathematics (up to solving simple differential equations and employing different integration techniques), physics (including material science, quantum mechanics with solving simplest Schroedinger equations and Special Relativity), computer science (including programming in Basic, C and Pascal), organic and non-organic chemistry (including solving problems for reactions kinetics such as time of a reaction and change of the balance between reagents and the product with change of temperature, calculating change in entropy, enthalpy etc), biology, history, Russian language and literature (including syntactic analysis of sentences, morphological and phonetic analysis of words), English language, geography and other minor subjects such as music.

There were some good teachers such as a physics teacher who often made interesting demonstrations such as powering a fluorescent lamp which he held in his hands with an electro-magnetic emitter located at a distance. So the the lamp being not connected to any electric source still emitted light. Or warming a closed bulb with water in the light of a projector that projected the bulb to the screen so to demonstrate the critical point of water: the boundary between water and vapor eventually blurred and disappeared as the substance was becoming a hypercritical fluid. On still another occasion he made an installation of consecutive polarizing filters in front of a projector to demonstrate the effects of polarization and that inserting one more filter in the middle can actually increase the amount of light falling to the screen.

It should be noted that the Russian government recently announced a simplification of the school curriculum with only "basics of Orthodox Christian culture" (a newly introduced subject) or "basics or Islamic culture" (in some regions), life safety (another newly-introduced subject), patriotic education and athletics will be mandatory with all other subjects optional, but not more than three. This came under great criticism in the society.