For decades, pudding-bowl bobs and army-type cuts were the only hairstyles allowed to be sported by Thai schoolchildren -- but now looser rules spell new freedom for classroom coiffures.
"I am embarrassed having this kind of hairstyle," 14-year-old Visarut Rungrod told AFP, running his hand over his close-cropped head, adding he plans to lengthen his locks as soon as possible.
"I will feel more confident when I go out," he explained.
Rules issued in 1972 compelled Thai pupils to have identical hairstyles -- a trim not below the earlobes for girls and a maximum five-centimetre length for boys -- until the end of high school.
But students are now hoping to flaunt their individuality after an edict by Thailand's education ministry in May scrapped the measure.
The issue, in a nation which emphasises collective culture over individualism, was sparked by an anonymous complaint by a 15-year-old student to the National Human Rights Commission of Thailand in 2011, saying the strict rules violated human rights and freedom.
"It made adolescent students lack confidence and lose concentration in studying," the student said in the letter, which won mass support across social media among teenagers.
The letter stirred debate in a country where the education system often faces accusations of promoting rigid conformity over creativity and independent thought.
Under the new rules, girls are able to grow their hair long -- although they will have to wear it tied back in matching ponytails -- while boys can grow their hair to the nape of their neck.
As fashions changed, a small number of schools had already allowed girls to grow their hair long, as long as it was kept tidy, but the May rule change has brought new-found freedom to teenagers across the kingdom.
Not everyone is happy. Some teachers and parents fear doing away with the traditional tresses is the start of a wider unravelling of Thailand's appreciation for conformism.
"They must all have short hair otherwise there will be a lot of varied hairstyles (in schools)," said 56-year-old father, Pornyudh Budhapongsiriporn, whose sons are 12 and 15.
"If most students have a short haircut, the rest should have short hair -- otherwise they won't fit in with society."
For parents like him, all is not lost in the battle to preserve conformity.
The government still gives teachers ultimate authority to decide their school's hair policy.
"Among our teachers and school committees, the resolution was that all students should have the old hairstyle," said Ratchanee Prapasapong, director of Makutkasatriyaram School in Bangkok.
"Though hairstyle has nothing to do with teaching, we see it as a kind of discipline for living together in society. It also shows that younger ones respect (and) still want to keep the traditional culture of older generations," she added.
Experts suggest that the new rule may indeed herald a wider move away from that traditional culture and say it has troubled the conservative older generations.
"They are very confused that all of a sudden students have long hair," Somphong Chitradub, an education expert at Bangkok's Chulalongkorn University, told AFP.
"But it (the freedom to grow their hair) develops children to show their real feelings -- it will make them feel good," Somphong added.
One key objection is that pupils will be distracted from their textbooks by the pursuit of funky new hairstyles, while some parents fear an increased physical awareness may push their children prematurely towards having boyfriends or girlfriends.
It is an idea rubbished by Somphong, who says those fears smack of paranoia as it is "inner discipline", and not hairstyles, that dictates pupils' application at school.
"Parents and teachers do not understand the real needs of the students, although they have good intentions by thinking for the kids," Somphong said.
"They should teach the kids about life skills and building self-discipline."
For most pupils, the issue is simply about choice and does not carry much wider social meaning.
"It depends on us how much we want to pay attention to studying or to beauty," said Pattanotai Tungsuwan, a 14-year-old female student with a silky black ponytail.
"For me I would rather pay attention to my studies."