Look, my girlfriend's son is starting the colegio next year so I do have a little first hand knowledge. Kids are put first and formost with the siblings, and with just a tad less priority in schools in which their siblings had graduated. The part about getting notified at the end of the year is true because they spend time placing students making sure that kids aren't separated and that as many get their first choice as they can.
The problem is that some schools in the city are much much more popular than others and are over enrolled where as others are under enrolled. Previously you had a bunch of people try to get their kids in the popular schools and then they weren't notified till mid november to december if they had gotten in, which then caused all the parents to have to run around looking for other schools all over the city.
Having the whole process computerized makes more since and is a lot more convenient for kids whose parents both work. I suppose that upper class families that have one wage earner and another stay at home parent who can wait in line to register their child during a work day have the luxury of complaining about diminishing parent - school contact, but if it bothers them that much, they can afford to pay a private school.
This is like saying that digital switching destroyed the personal contact with your local telephone operator.
