Significant changes have been made to the Code de la sécurité routière. These new measures, including the child booster seat, stem from Bill 165 - Loi modifiant le Code de sécurité routière et d’autres dispositions passed in April 2018.

Starting April 18, section 397 of the Code de la sécurité routière will read as follows:

397. In a moving road vehicle, any child under 145 cm in height or under 9 years old shall be installed in a restraint system or a booster cushion in accordance with the regulations made under the Loi sur la sécurité automobile (Statutes of Canada, 1993, Chapter 16). The restraint system and booster cushion must, in accordance with the manufacturer's instructions, be adapted to the weight and height of the child and be properly installed in the vehicle.

However, the use of a restraint system or booster cushion is not mandatory:

for the child occupying a designated seating position, within the meaning of the regulations made under the Motor Vehicle Safety Act, that the vehicle manufacturer has not equipped with a seatbelt, provided that no seats are provided a seat belt is available;
for the child authorized by the Société, in accordance with section 398, to use a restraint system other than that provided for in the first paragraph. [...]
As a result, children will be required to sit in a car seat adapted to their weight and height until they reach the age of 9 or until they are 145 cm tall.

However, child booster seats or the addition of seat belts or harnesses are not mandatory because school bus manufacturers have not fitted seatbelts. At this time, none of the federal or provincial standards require a school bus to be equipped with a seatbelt.

If you have any questions about this, please contact Christine Deslauriers at (418) 476-8181 ext. 209 or at cdeslauriers@federationautobus.com