4 years in and 4 years out ruling for TFW is strictly applied. Immigration Canada is very strict for this implementation, no other reasons you can stay after the contract. Going back to school as international student is not grounds for you to stay. If you go underground, that is the worst decision you can make and immigration will give heavy penalty and you cannot go back to Canada. You have to follow the immigration laws and regulation. This is one way to protect their own citizens and limit the inflow of immigrants in Canada.