Sally Kincaid, the Wakefield branch secretary of the National Education Union (NEU) said head teachers should be more concerned about the wellbeing of their students than their uniform.
Councillors have criticised academies for insisting pupils wear expensive branded items with school logos, at the expense of more affordable generic smart clothes which can be bought from the high street.
The report said some schools did help parents struggling to meet costs, but that support schemes were not widely publicised enough.
Speaking at a meeting on Thursday, where the issue was discussed, Mrs Kincaid said: "Wouldn't it be nice if, instead of checking kids' uniform and shoes as they come through the gate, asking them if they've had breakfast or not?
"This obsession and control (with uniform) has got to stop.
"As a teacher I want the kids sitting there and learning. I don't want to spend 10 minutes saying 'Tuck your shirt in, do this, do that'.
"It's about inclusion."
The report was critical of schools' punishment of pupils who turn up in the wrong uniform, and said parents' inability to afford the correct clothes was leading to bullying and truancy.
Labour councillor Josie Farrar, who led the cross-party investigation behind the report, said some pupils were put in so-called "reflection rooms", where they are forced to work alone for the day.
She told the meeting: "It's a box with a board on the left and a board on the right.
"They're allowed out three times a day to go to the toilet. They have to have their lunch within it.
"Let's not get bogged down in the idea that it's a reflection room.
"What are they supposed to be reflecting on? That their parents haven't got enough money to buy them uniform."
Councillor Farrar said some academies were recommending parents visit uniform exchanges, which are run in a similar way to foodbanks, if they were struggling to pay for school clothes.
But she added: "That's putting pressure on volunteers. They don't get paid to run a uniform exchange.
"They're relying on people donating, and it's amazing people do donate, but a lot of parents are selling old uniform on because they're struggling and they need the money.
"Uniform exchanges rely on someone giving you space for free, because there's no funding for them.
"Then they need the resources to sort clothes out, wash them and redistribute them. All these things need taken into account.
"There's massive gaps in these systems, but the government is using charities to fill those gaps and that's not acceptable when children's education is at risk."
Local Democracy Reporting Service