Due to copyright laws, access to free online versions of French textbooks is usually quite limited. Learnalberta, the government website, has online versions for students with disabilities but, again, because of copyright laws, the guidelines for those who qualify are very strict.
For most grades, the options generally seem to be as follows:
Math: Purchasing a digital copy from the publisher for $9.98 for one-year access or purchasing a textbook $90+.
Social: Purchasing a textbook for $95 +.
Science: This text appears to have been freed from copyright because it is available easily by doing a google search.