One told The Mail on Sunday: "He decided to film the teacher because he wanted to show what was going on in schools today for simply stating there are only two genders.
"He has nothing against anyone who identifies as LGBTQ, but completely disagrees that there are more than two genders and that it's a social construct.
"He believes telling kids that boys are girls and girls are boys is a very dangerous thing and wanted to get his views across to the teacher.
"His view is that scientifically there are only two genders. This new gender theory that there are unlimited genders is something that should be discussed and debated – not just thrown into a class discussion and if you disagree you get kicked out of the room."
The incident took place when the teacher logged on to a website and found only male or female gender types listed as options, which he claimed was "old fashioned".
When the schoolboy disagreed, he was ejected from the class. After being allowed back, he secretly filmed the teacher. In the video, which has been watched on YouTube more than 90,000 times, the teacher can be heard telling the pupil: "You're entitled to your opinion."
During an exchange, the pupil says: "I think it's silly to have anything other than two genders, Sir."
The teacher then urges: "Could you please keep that opinion to your own house? Not in this school."
The three-minute clip triggered a furious debate online, with many saying the boy had been unfairly treated, while others insisted that the teacher was in the right. According to an education source, the boy was suspended for breaching school policy by secretly filming the teacher.
An Aberdeenshire Council spokesman said the public sector has a legal duty to show "due regard" to certain "protected characteristics" – including age, sex and "gender reassignment".
He added: "It is important to understand the context of any video clip taken without a person's consent. In our schools, fostering good relations among different groups can be a real challenge but our aim is to support a fairer, inclusive environment for all."
Earlier this month, London-based Pearson Edexcel exam board was accused of bowing to demands from transgender activists after swapping the word "sex" for "gender" in a UK GCSE biology paper.
Lincolnshire businessman and former police officer Harry Miller also found himself investigated by police for "hate crime" for "liking" a poem on Twitter questioning transgenderism.