At least in my country (Romania), the norm in all public schools is to have the same set of ~30 children you'll go to school every day with from grade 0-1 (6-7 years old) to grade 8 (14 years old). Since there are very few to no electives, you'll spend ~all of your time in school with all of these kids every day for 8 years - and virtually everyone in the country has this experience (private schools are very rare).