Schools are being urged to ban unnecessary or excessively expensive items from their uniforms.
The call is being made by MSPs on Holyrood's education committee who are looking at the link between poverty and attainment among pupils.
They are calling on schools to "poverty proof" uniforms and also to question the assumption that families have access to computers at home.
The Scottish government said it was spending £750m to improve attainment.
The plea for cost curbs follows an inquiry by the committee, which left some MSPs "appalled" about the number of youngsters attending classes while hungry.
They hailed the work by some councils, including Glasgow, which increased its free meals provision to include pupils up to P4, while others, such as North Lanarkshire, are tackling "holiday hunger" by offering youngsters lunches during holidays.
But MSPs voiced concern about the cost of some items of school uniform, and warned that moving to online payments for school dinners or trips could disadvantage families without access to computers.
Committee convener James Dornan said: "We heard time and again that teachers are increasingly seeing children who are affected by poverty, including children coming to school hungry.
"That this is an increasing problem in Scotland and is utterly appalling, but we know that this is something that schools cannot tackle alone."
'Penalised or excluded'
Labour education spokesman Iain Gray said: "The rising costs of school uniforms and trips leaves far too many families struggling to cope.
"It is important that schools and local authorities take this into consideration and make a concerted effort to drive down prices as much as possible."
Green education spokesman Ross Greer said: "What we are often seeing is that pupils from low-income families are being penalised or excluded because their school has failed to poverty-proof its uniform policy, or worse, parents being forced to choose between feeding their children and buying them the clothing required."
MSPs made a number of recommendations, including calling on councils to ditch costlier items associated with uniforms, therefore allowing parents to buy unbranded garments from supermarkets.
The Scottish government was also urged to survey councils to establish which charged for in-school activities, and how much the charges were.
Ministers said they were providing £120m directly to head teachers under the Pupil Equity Fund.
A spokesman also added: "We are investing £750m during this parliament to tackle the poverty-related attainment gap and ensure every child in Scotland has an equal chance to succeed.
"Our Tackling Child Poverty Delivery Plan is backed by a multi-million package of investment.
"It sets out action such as support for after-school childcare, access to meals during holiday time, and increased help with the costs of uniforms."
A spokesperson for the UK government said: "The proportion of people in Scotland living in absolute poverty is at a record low, including for children. Poverty rates are falling while the employment rate is increasing, and work remains the best route out of poverty.
"We know there is more to do to ensure that every child gets the very best chances in life.
"Our welfare reforms offer parents tailored support to move into work, ensuring that even more families can enjoy the opportunities and benefits that work can bring."