The Government's competition watchdog has issued an open letter to all headteachers urging them to recognise that these exclusive deals are "not giving parents value for money".
The CMA found in some cases parents were paying up to £10 extra per item because they were buying from the schools' appointed suppliers.
Anne Pope, the CMA's senior director of enforcement, states in the letter: "Schools should make sure that there is competition for the supply of school uniforms to parents.
"Customers benefit from lower prices, better quality goods and services, new and innovative products and greater choice."
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The CMA has also encouraged other suppliers and retailers who are struggling to sell uniforms to get in touch.
These retailers, including supermarkets such as ASDA, Tesco and Aldi, offer similar clothing to suppliers appointed by schools, but for a much lower price.
A CMA spokesman told The Guardian: "This letter is primarily addressed to state schools, including academies and free schools. But we do also encourage fee-paying schools to review their arrangements."
Pope, added: "Buying school uniforms can be very expensive and particularly hits low-income families and those with a number of children, so it is important parents and carers are able to shop around."
The CMA also issued a call to action for headteachers asking them to ensure they take on board parents' and carers' views on the prices of school uniform, and "prioritise providing value for money" when selecting school uniform suppliers and retailers.
David Burgess, chair of The Schoolwear Association said while price is important, the first priority is for children to have good-quality uniform as they wear it for up to ten hours a day.
He said: "We are anxious that the focus on school uniform should not be solely on price at the expense of poorer quality.
"Well-made, long-lasting uniform is not only better value in the long term but also the most environmentally sustainable option.
"There are some benefits to sole supplier arrangements, particularly because a single supplier is dedicated to the school and required to stock uniform all year round in all sizes.
"When there are two or more suppliers, that sense of duty diminishes, and the school has less power to demand best value and service levels."
Burgess said if a school decides on a sole supplier arrangement, they should put contracts out to tender where quotations can be compared on quality, service levels, year-round stocking, ethical sourcing and price.
He also said The Schoolwear Association has lobbied the government to remove VAT on school uniform and to enable a voucher scheme, similar to childcare vouchers.
Every parent of a thick-haired kid's worst nightmare, lice are insects that feed and lay their eggs on the human scalp. (Itchy yet?) How it gets around: Head lice is spread through hair-to-hair contact or by sharing things like hats, headphones, and hair brushes.Symptoms: The first sign of head lice is usually an itchy scalp. Check your child's hair for lice and their eggs (nits), which are usually whitish in colour and found close to the base of the hair shaft. The Rx: Suds up with a shampoo containing an insecticide. More and more resistant insects have been found in recent years however, and parents are turning to special heat treatments to eradicate these "Super Lice".Post-shampoo combing is also key, so be sure to get a steel lice comb (the plastic ones are useless -- don't even bother). Prevention: Watch out for group selfies! Scalp to scalp contact is a sure fire way to aid and abet these itch-causing pests.
Hand, Foot And Mouth Disease(02 of04)
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Known for causing painful blisters on the inside of the mouth, the bumpy, red rash can also affect hands, the bottom of feet, and genitals. How it gets around: The gross factor here is that the virus lives in the intestines and is spread through unwashed hands and surfaces contaminated with feces. Symptoms: Small, fluid-filled blisters are usually the first sign of HFMD but can be hard to detect if only in the child's mouth. Other signs include fever and flulike symptoms. The RX: There is no treatment for HMFD outside of managing the symptoms with children's acetaminophen or ibuprofen. The child is considered contagious and should stay home from school as long as a fever and open blisters persist. Prevention: Encourage your child -- and the whole family -- to wash their hands often. Note to parents: The virus can live in your child's stool for up to two weeks after the blisters have subsided, so be vigilant about washing your own hands after changing diapers or helping older children in the bathroom. HFMD in adults, although more rare, is decidedly more painful!
Pinworms(03 of04)
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This one's not for the faint of heart! Pinworms are parasites that hatch in the human intestines after eggs have been ingested by the host. Once hatched, the females then travel out through the child's anus where they deposit new eggs (cringe). How it gets around: Upping the ick factor here is that pinworms are spread when your child scratches their itchy bum, trapping the eggs under their fingernails for easy transfer onto surrounding surfaces. Doubly gross is the fact that the eggs can survive for up to two weeks outside of a host! Children can catch pinworms simply by putting their fingers in their mouths after touching an affected surface. Tellingly, the pests are most prevalent in school-age children between five and 10 years old. Symptoms: Your child may have a stomach ache and/or an itchy bottom. The worms can also be visible on your child's anus at night when the females are most active. The RX: Doctors can prescribe an anti-worm medication and there are over-the-counter treatments as well. Prevention: Children should wash their hands often throughout the day and avoid putting their hands in their mouths.
Impetigo(04 of04)
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This bacterial skin infection causes blistering and sores and occurs most commonly on the face, neck and hands of children two to six years of age. It's gross because the blisters can be hard to look at, depending on the severity of the infection. How it gets around: Impetigo is highly contagious and spreads through skin to skincontact or by simply touching something that someone with impetigo has also touched. Symptoms: There are two types of impetigo: 1. Non-bullous, which starts out as tiny blisters that burst, leaving "weeping" patches of skin that eventually crust over;2. And bullous impetigo, characterized by larger, fluid-filled blisters that turn cloudy and stick around longer than those associated with the non-bullous form. The RX: Treatment depends on the type and severity of the rash. An over-the-counter antibiotic cream can work well on some non-bullous cases whereas oral antibiotics may be required for more serious cases or bullous impetigo. Prevention: As with most communicable diseases, hand washing goes a long way in prevention. Because the bacteria that cause impetigo can also enter the body through existing scrapes, cuts, or burns, it is important to keep these injuries covered and clean, particularly in the classroom setting.