Vidyarambha Sanskar means starting the education of a child. It typically beigns in the fifth year. When the mind of the child was prepared to receive education, the Vidyarambha Sanskar is performed to mark the beginning of the education to gain knowledge, and alphabets are taught. The Vidyaramabh Sanskar has several names, it is also known as Akshararambha, Aksharasvikarana, Vidyarambha and Aksharalekhana. As it's very name suggests, it was more cultural than natural. It originated at a very high stage of civilization, when alphabets were evolved and utilized for reading and writing purposes.
We do not find much details as to how this Sacrament was motivated. In Uttarakanda of Valmiki Ramayana there is a lone reference to this ceremony being performed by Sage Valmiki to Lava and Kusa after the Chaula (tonsure) ceremony starting primary education in many sciences before the commencement of the study of Vedas. Vedas mention briefly the need for Medhajnaana (Apara Vidya) for all individuals before Brahmajnaana (Para Vidya).
The Vidyarambha Sanskar is performed in the fifth year of the child according to Sage Vishvamitra. It can be postponed to a later year but must be performed some times, before the Upanayana Sanskar. When the sun is in Uttarayana after Makara Sankranti, an auspicious day is chosen for its celebration. The child is given a holy oil bath, exposed to incense (dhoopa), and dressed up with new clothes and jewels. Vaishnavites propitiate Narayana, Lakshmi and Saraswati after worshiping Vishwaksena to remove all obstacles. Homa is then performed with Medhasookta as given below. After this Homa the teacher, facing towards the east, performs the Akshara Aarambha of the child who faces west. The Samskara consists of writing and reading both. Saffron, turmeric and other substance are scattered on a silver plank and letters are written with a gold pen. When not affordable it is done on grain of rice in a silver platter. I did it on sand and my Guru was my mother. Normally father does that in the absence of the family Guru. Followers of Siva start the worship with Ganesha pooja and propitiate Siva and Parvati, universal parents and Lord Subhrahmanya, Guruguha. Then the child worships the teacher or whosoever initiates writing. The teacher makes the child write three times each letter starting with AUM and Aa and the first alphabets of names of Gods. The child is made to read what it wrote thrice. The child is then made to offer clothes and money to the teacher (as Gurudakshina). It then goes round the deities three times in circumambulations. The teacher and the elders then bless the child. Elderly married woman living with husbands wave colored water of vermillion in which a lamp glows before the child and bless the child with turmeric colored rice (Akshat). The teacher is honored as the chief guest by tying a turban on his head and the invitees are lavishly feasted as is customary in any happy occasion or ceremony.