One of the reasons that the US has a summer break with 2 to 3 months off was for the kids to be at home during harvest. So that the crops could be gathered and preserved for the rest of the year. So originally the kids worked on the farm or orchards etc during this time, even if they couldn't harvest, they could tend the animals etc. while the harvest was going on. To say that the kids need the summer break to be kids and play is false, as it happened as a side effect as the harvest changed from manual to machine labor.
At this day and age, when more and more parents both work to support the family, I can see how a full school year can help in a variety of ways. First the weekly schedule would not have to change during summer, day care would be more consistent, I don't know about your areas, but here some kids can't get day care during the summer months because they fill up and no additional companies start up since 9 months out of the year they wouldn't have enough business to keep the doors open. Secondly, teacher salaries would be more consistent with all other businesses, I know that some teachers take no salary during the summer months and others average their paychecks to include the summer months. That discrepancy and additional accounting would be streamlined. Third it would better prepare students for the work force, no summers off, continuing learning and productivity all year round.
Of course vacations would have to be planned, so in the school days off there would have to be X number of days figured in to the curriculum for the students to be off for vacation, just like PTO for work etc.. But this would eventually normalize out the vacation spots, as some would take theirs in March, or April or August and September, or maybe other times of the year. Parents would not have to schedule their vacations during the shorter vacation time of summer school vacations.
