Dilip Ahluwalia, 56, owns the Gravesham Uniform Centre run by his son Amit, 23, in Barrack Row, Gravesend.
Mr Ahluwalia has put up a large banner outside his shop saying “RIP OFF School Uniform Campaign” and plans to display the name of a different school he is unhappy with each fortnight.
The first name he has put up is Mayfield Grammar.
School Uniform Shop, Barrack Row, Gravesend - Jay Sandhu and Dilip Ahluwalia
They are not the official supplier of uniform for any school, and Mr Ahluwalia Snr believes parents are being denied value for money.
Many schools have contracts with companies to supply their uniform.
Without that agreement, Mr Ahluwalia is not allowed to sell their clothes, even though he says he is able to embroider badges and crests.
He said: “I just want a level playing field. It’s not being fair to me or the parents.”
Department of Education (DoE) guidelines say when schools consider where uniform should be bought the highest priority should be given to how much it could cost parents.
Mr Ahluwalia claims he can provide the school’s kilt for £22.08, beating the prices of Mayfield’s two recommended outfitters – The Sewing Shop in Echo Square and Longfield Wools, in the St George’s Centre – by at least £6.91.
The school’s tartan is protected by copyright and is on the Scottish Register of Tartans. Mayfield head teacher Elaine Wilson said: “Mayfield Grammar School regularly reviews the quality and price of its uniform to ensure best value for parents.
“The school supports the local economy. Our current suppliers are local businesses and the school complies with Department of Education guidelines.
"We have no plans to increase the number of suppliers. We have written to Mr Ahluwalia and informed him.”
Mr Ahluwalia, who also runs Traditional Shoe Repairs in Barrack Row, said: “We want a healthy competition.”
He is consulting lawyers about whether he can take action against the schools. He said: “We’ve not got a lot of money in Gravesend. This isn’t Eton.”