Initially, once the harvest season began in Jan, schools closed and students were forbidden to continue with their education and learn the vedas after Jan. It was considered a sin. Imagine! the very concept of formal education was considered a sin for 6 months every year. I want this law brought back. This is an awesome law. Later, this practice was considered inefficient and students were allowed to rehearse, whatever they learned in the first six months, from Jan/Feb to Aug/Sep. So the students rehearsed during spring and summer semesters whatever they learned in Fall & Winter :-) and when they began the next new academic year, they sought atonement for such a sin.
Upakrama is a ritual done on the first day of the academic year every year. It is done till date in the 4 southern states, Maharashtra and Orissa. It consists of Yajnopavitam change, seeking atonement and vedic-style hair cuts for the new academic year. The second day of the academic year involved reciting the Gayathri Manta - 1008 times. While the Upakrama date varied depending on the vedic school, the Gayathri recitation date was the same for all schools. Learning of the vedas never stopped until a person died. So a person regardless of age or marital status did this every year. As mentioned before, each of the 4 vedic schools had different start dates With Sama Veda having the latest start date in September (on the day of Vinayaka Chaturthi). I am not sure why they got such a large summer vacation. Maybe they were slow learners and needed more rehearsal time :-) or maybe Sama veda with all its musical intonations was difficult to master and hence the students needed time. I have always been curious about the relationship between Vijayadasami and Avani Avittam. Vijayadasami is considered the day of beginnings by most people, whereas Avani Avittam had already marked the beginning of school. So what is the deal here?
Avani is the Tamizh name for the Shravana month and Avittam is the star that appears on the month of Avani. The Panchangam (calendar) is used to decipher the date on which the Avittam star will appear. It is also believed that this was the day in which education as a concept began. Following the creation of the world - it is on this day that Brahma, the first being, was supposed to have learned the Vedas from Lord of Knowledge - Hayagriva - thus becoming the first ever student.
P.S: Raksha Bandhan, is celebrated in N.India on the same day (sharavana purnima) as Avani Avittam every year. I do not know much about the significance of this day except that it is attributed to many legends including tying of sacred thread by Sage Brihaspathi on Lord Indira's wrists, Tying of sacred thread on the wrists of King Bali by goddess Lakshmi, Yamuna tying raakhi to Yama etc.