The head of the NZSTA - the body which represents the views and provides services to the parent-elected boards of trustees who govern the nation's schools - has also sent teachers a directive to improve their communication with parents and caregivers.
That includes making "good news" calls to parents when children impress in the classroom.
Kerr said for many parents their school experience wasn't a good one so talking to teachers about their children was difficult. "Parents do not get many 'good news' calls which is why many people answer the phone hesitantly when they know it's a call from the school," Kerr told the Herald on Sunday.
"In their mind, a call from the school is unlikely to be a 'good' call. It would be great if schools phoned families to talk about something positive, rather than, 'Oh no, what has gone wrong'?"
Kerr's guidelines also warned teachers against "slugging it out" in emails.
"If a parent/caregiver has called or emailed and is angry, emotional or offensive, don't be tempted to get into a battle on the phone or by email. Instead, suggest a meeting."
Kerr recommended teachers engaged with parents regularly during the year by posting assignments and lessons online and turning up to students' sport or cultural activities.
"Some principals get out in the rain and follow their rugby team or their netball teams on a Saturday and the relationship between those people and their families is amazing because they've taken the time," she said.
The primary teachers' union, the New Zealand Educational Institute, said in many cases the dress code advice was impractical as teachers had to dress in ways that best suited their jobs.
"Every day this involves things like sitting on the mat, climbing on ladders to put displays on walls, running around on the sports field, mixing paints, and so on," national president Louise Green said.
The secondary school teachers union said communicating with families was important but there didn't seem to be much thought from the NZSTA about how adding extra tasks could work practically.
"Given teachers are in class four or five hours a day, and for secondary schools there are at least 150 different sets of whanau to connect with, how do they expect us do it?" Post Primary Teachers' Association president Angela Roberts said.
"Wouldn't it be great if NZSTA were lobbying for reduced class sizes? It would be much easier to build relationships with families if you had 25 kids in your class rather than 35."
