"The danger with this is [students] get into the big, bad world and they find out they're not so good. This is a tremendous blow to their self-esteem," he told the Herald on Sunday.
He said a lack of honest, helpful feedback was leading to a confusion for children.
Giving children regular, constructive feedback about how to improve was a better policy, he said.
"We need to say to kids that they can do this, they can't do that but to move their learning forward they need to do this, that or the other. What we don't say is you're good or bad at something," said Dinham.
This reinforced a valuable message that effort brought reward.
At an education conference in Sydney last month, Dinham criticised techniques used in Australian teaching.
Talking to the Herald on Sunday, he added his concerns about the increased use of e-learning in schools on both sides of the Tasman.
He believed the use of devices, and the benefits they could provide to pupils, was largely untested.
Head of the primary teachers' union, NZEI, Louise Green agreed, saying adopting an untested learning style in the classroom put at risk the ability to identify and address diverse learning needs, she said.
The union was working with the Ministry of Education to come up with a blueprint about best teaching practice.
Last month, the Herald on Sunday revealed Auckland school children may have to play for the opposition at sport if they're beating them by too many points.
The Howick Pakuranga Principals' Association is introducing a fair play charter to East Auckland primary schools to encourage students, coaches and parents to play nice. A clause allows coaches to intervene when the points differential is 40 in rugby, 15 goals in netball and seven goals in soccer.
The charter was being introduced because children could be devastated if losing margins were too huge.
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