Our school is about the entire community, not just the teachers and the children attending school. I don't believe a child has the opportunity to reach their full potential without collaboration between the school and the home. I also believe that it is very valuable for children to see their school community function effectively on a social level - that is, parents, siblings grandparents, uncles, aunts... all getting along and enjoying each other's company.
This is exactly what I wanted to say! To me, being part of the community and participating in community events is a big part of learning as well. At our school (a smallish rural school), younger siblings are encouraged to come in to the classroom and explore, they're encouraged to go and sit on the mat with the children at the end of the day etc.

Sure it can get a little chaotic, and perhaps your school could of managed things a little better, but I really think it is extremely important to have family input, not just from parents, but from siblings of all ages, and extended family too!