My daughter has been mixing with other parents and children from the school throughout the holidays. Sharing the children around, meeting up at the park etc. The families are not really limiting their interactions from what I can see. High school students heading off out together to the beach etc. Maybe some teachers might have managed to remain out of circulation.
While true it is also the case that:
New students start school for the first time in prep.
Students in year 7 will often be at new schools and in the main drawn from many different primary schools.
A number of students change schools for various reasons.
Over summer kids mainly mix with their close mates. Back in school they mix with the whole class and beyond including those that they do not socialise with.
Many schools will blend year classes each year. So depending on the size of school the class maybe quite different.
For senior years many, if not most, schools teach by subjects, and the form class may only start the day rather than be all day. After that you split by the subjects chosen. So the pool of students mixed with magnifies.
Then add the co_ corricular activities like music, sport, plays etc and you get more mixing again.
Then after that for many secondary students they will go to and from school by public transport thereby not only mixing year levels, but also mixing with multiple schools.
Then add in teachers etc.
So overall I personally believe there will be a lot more mixing of people that are not currently mixing.