For lower classes this essay on holi has to be made a little bit simple.
Main Significance of Holi:
In Vaishnavism, Hiranyakashipu is the great king of demons. He had been granted a boon by Brahma. This boon made it almost impossible for him to be killed. The boon was due to his long penance. After it he had demanded that he not be killed "during day or night; inside the home or outside, not on earth or in the sky; neither by a man nor an animal; neither by astra nor by shastra". Consequently, he grew arrogant and attacked the Heavens and the Earth. He demanded that people stop worshipping Gods and start praising him.
Other significance is that Prahlada, was a devotee of Lord Vishnu. In spite of several threats from Hiranyakashipu, Prahlada continued offering prayers to Lord Vishnu. He was poisoned but the poison turned to nectar in his mouth. He was ordered to be trampled by elephants yet remained unharmed. He was put in a room with hungry, poisonous snakes and survived. All of Hiranyakashipu's attempts to kill his son failed. Finally, he ordered young Prahlada to sit on a pyre on the lap of his demoness sister, Holika, who could not die because she also had a boon which would prevent fire from burning her. Prahlada readily accepted his father's orders, and prayed to Vishnu to keep him safe. When the fire started, everyone watched in amazement as Holika burnt to death, while Prahlada survived unharmed, the burning of Holika is celebrated as Holi.
In Uttar Pradesh the famous Lath mar Holi is played in Banaras (Varansi) in the sprawling compound of the Radha Rani temple. Thousands gather to witness the Lath Mar holi when women beat up men with sticks, All of them sing Holi Songs and shout Sri Radhey or Sri Krishna. The Holi songs of Braj mandal are sung in pure Braj Bhasha.
It is adding to pollution. The world is fighting against global warming where as the Holika Dahan is just an opposite parameter to global warming check up. But due to religious impact nobody politically can impose any law. It is the people who will decide about this..
Whatever may be it gives us great energy to becoming united. And a lot of enjoyment is attached with this festival. I like it from the bottom of my heart.