Fundational Myth: the sacrifice of the Purusha
One of the most important myth in Hinduism is the creation of the world through the sacrifice and dismembering of the Purusha, or Primordial Man. This myth is found in the RgVeda, the hyms collection of the larger Veda Corpus (see below).
This myth is of particular importance because it provides the religious justification of the structure of the Hindus society, that is, the division in social groups (Varna, see below), the backbone of the Indian caste system.

Main doctrinal tenets: the Varna division of society and the Indian caste system
The Varna (lit. color) division is the traditional social stratification of India. It divides the Indian society in four functional segments hierarchically arranged:

the Brahmanas:Brahmin priests and scholars, whose color is white, expressing purity.
the Kshatriyas: kings, administrators, warriors and soldiers, whose color is red, symbolizing blood.
the Vaishyas: cattle herders, agriculturists, artisans and merchants, whose color is gold, symbolizing gold and harvest.
the Shudras: laborers and service providers, whose color is black, symbolizing the earth.

Certain groups now known as "Dalits", were excluded from the Varna system altogether, ostracized by all other castes and treated as untouchables. Dalits and Shudras, as the lowest strata, are excluded from reading the Veda Corpus, then excluded from salvation in this life. They can still hope for a rebirth in a better Varna.
The System of Varna implies strict regulation in terms of social relationship. Members of a certain Varna are forbidden to marriage or even eat together with members of a different Varna.
Each Varna is divided in multiple Jati (lit. birth) which is a term used to denote the thousands of local closed social groups. These groups are hereditary and are classified on the basis of their ritual, territorial, and/or occupational identity.
Varna and Jati build up together a Indian caste system which envisions a society where each person has their own collocation, duties and rights. This idea of social order has a religious and sacred connotation, as the foundational myth explained above shows, and it is included in the concept of Dharma (see below).
However it is important to state that this system does not preclude any social mobility: a Jati can move in the hierarchical scheme of society, and an individual could move to another Jati through inter-Jati marriage.
Even if the discrimination based on caste is prohibited in the article 15 of the 1950 Indian Constitution, it is still a common custom especially in marriage.

Main doctrinal tenets: the concept of Dharma
Dharma is a pivotal concept in Hinduism, it means "law" but it should be understood as the cosmic order which sustains the whole universe. Dharma, in Hinduism, is an organizing principle that applies to human beings in solitude as in society. It refers to the order and customs which make life and universe possible, and includes behaviors, rituals, rules that govern society, and ethics.
Dharma is that which all existing beings must accept and respect to sustain harmony and order in the world.
Therefore it is not surprising that Hindus, when translating the world "religion", tend to use the expression Sanatana Dharma (eternal law).
Dharma has two poles. The first is the general Samanya-Dharma (the common norm), basically a set of universal values towards which everyone is supposed to comply. These are non-violence, veracity and generosity. But the real code of conduct for the pious Hindus is represented by the Sva-dharma (the own-norm), which includes the religious duties, moral rights and duties of each individual on the basis of his place on society, that is, on his Jati (see above).
Therefore is easy to understand that, for the pious Hindu, Dharma is -for example - the Varna and Jati system (see above) itself, and the existence of this system is conceived as being "natural" as well as sacred, as it is explained by the excerpts from the Bhagavad Gita (see below).

Sacred texts and other main texts: The Vedic Revelations
The textual foundations of the Hindus religiosity are found in the corpus called Veda (literally [sacred] science). Originally they were a large set of doctrines, composed roughly around the 1500–1000 BCE. orally transmitted and put in written form only in recent times (I sec. BCE). They are considered not human creation, and supposed to have been directly revealed to the Rishis (sages, or seers) by the gods themselves. They are conceived as revealed truths (Shruti). For this reason, also their language is considered sacred.

Sacred texts and other main texts: the Bhagavad Gita
The Bhagavad Gita, is a 700-verse scripture that is part of the larger Hindus epic Mahabharata. It is a sacred text of the Hindus. Theories on the date of composition vary considerably. Scholars accept dates from fifth century to second century BCE as the probable range.
The Bhagavad Gita is set in a narrative framework of a dialogue between prince Arjuna and his guide Lord Krishna. Facing the duty to kill his relatives, Arjuna is exhorted by his charioteer, Kṛiṣhṇa, among others, to stop hesitating and fulfill his duty as a warrior and kill. Inserted in this appeal is dialogue about methods and ideas concerning the attainment of liberation from the cycle of rebirth.
The Bhagavad Gita presents a synthesis of the concept of Dharma and ideals of liberation.

Analysis of the sources
Source N° 1
Rgvega X, 90
The primordial man, Purusha, is huge. He is simply everything - and more: What was, what is, and what will be. Only a quarter of him has materialized in the human world. The remaining three quarters of him are in the world of the gods as a hidden potential. Almost imperceptibly, the text goes on to tell the myth about how Purusha became this world. From the sixth stanza, we see that it happened because he was the offering. In primordial times the gods sacrificed Purusha as the first offering ever, the universal sacrifice that became the model for all later sacrifices. It contained the three seasons in India, and once the sacrifice had been made, everything was born out of it: the animals in the air, in the woods and in the village, i.e. the birds, the wild animals, and domestic animals (stanza 8), the rituals, hymns, mantras, traditional metrics and sacrificial formulas (stanza 9), the different kinds of livestock (stanza 10).
Together with these components of the world, also different kinds of human beings, namely the four social groups (varna) are created. They are even created from different parts of the primordial man: Brahmins (priesthood) from the head, the warriors (Ksatriyas) from the arms, the Vaishyas (i.e. the productive part of the population, such as peasants and artisans) from the thighs, and Shudras (people that service other people) from the feet. In this way, the social groups form a hierarchy, and it is quite clear that this is the world according to the Brahmin priests - with themselves at the top, due respect to warriors, and the rest of the population below with increasingly lower status.
This social order is perceived as just as fundamental as the physical organization of the world; the moon, sun, and a number of gods were formed out of Purusha, and space, sky and earth were also made this way.

Source N° 2
Bhagavad Gida ,ch. 18. 42-47
In this excerpt we have a more detailed explanation of the four classes (Varna) of the traditional Hindus society. But from the stanza 45 the text states clearly that performing one's natural work (that is, pertaining to his/her class) is tantamount to worship the Supreme Deity  and to attain perfection. Moreover, the stanza 47 explains that is even better to do a work of low quality, but nonetheless still inside the duties of one's own class, rather than do a superior work which does not pertain to one's class. A social class is, then, conceived as a inherent nature, and the complying with this order is a matter of sacred importance.

Intercultural & Interdisciplinary information.
(Civic Education, History)
NOTE: the subject of caste discrimination in India should be handled with care in order to avoid biased prejudice. It is a traditional view expressed by official ancient texts, while the reality of nowadays India is much more complicated and changed.
Nonetheless, the idea of equality of men typical of the Enlightenment is quite antithetical to the traditions of India. Also in nowadays India, there is the common idea that duties come before rights, because a society is considered to be functional and healthy when each segment works smoothly inside its compartment.
Pupils should be made aware of these differences with the Modern western idea of society, of individual, and of fulfillment of the individual. Pupils should be encouraged to look behind to find the historical sources of these ideas, such as the Enlightenment and the Declaration of the Rights of Man and of the Citizen of 1789. It could be a chance also to start a discussion on Human Rights and freedom of Religion in the context of Civic Education.