The business has become so competitive that book agents have reported buying bulletproof vests to protect themselves from possible assassination attempts by rival dealers.
Textbook publishers have been buying off headteachers with cash payments and free plane tickets to get their books on the required reading list - even though schools are supposed to use only books accredited by the education ministry.
Commission fees of up to 45 per cent of the book price are paid out by publishers, with the primary market said to be the most profitable. Teachers even band together to increase their negotiating power.
"When we submit our textbook proposals to schools they simply ask how big a commission fee we are offering," said one book agent.
As a result parents are having to pay two or three times ore for books published privately in order to cover the hidden kickback costs.
The education ministry this week sent out stern letters to schools using non-accredited books, telling them to take them back from pupils, re-order only authorised books and return the difference in cash.
Teachers say the order is pointless since the sale bribes have already been shared out and it will be the pupils' parents who pick up the tab.
The ministry has threatened to discipline school administrators if they fail to abide by the regulation. Publishers printing such books may also be fined.
Most official books are supplied by a state-licensed publishing house, have an embossed emblem and are two to three times cheaper than privately-published material.
Although under-privileged children receive free textbooks many better-off parents have to pay by instalment to cover the cost of buying books for their offspring.
International news, 16