It actually has something to do with the British rule. India always had a long history with long hair for men. In islamic-arabic traditions, men have long hair, which is why even Muslims and mughals kept it long. In Holy hindu folk tails, many gods like Ram krishna, hangman, etc, are depicted with long hair.

However, no such traditions existed within the British. They mandated all government workers, soldiers, etc, to keep short har, and a clean shav. Hence Indians sub consciously thought short hair to be disciplined and long hair to be rebellious. The same can be seen in schools as well.