Latvian citizen here with basic legal knowledge.
There's no EU-wide "fair use" clause for copyright and nothing quite like it in Latvian law. By the way, the law is officially published on www.likumi.lv in HTML form, a sibling post here links to a doc file at another governmental websites, but while other websites may re-post laws for convenience, it's www.likumi.lv that is official.
Section 19(1)(2) of the Copyright Law states that there's no copyright violation if copyrighted material is used for educational purposes in accordance with Section 21. That's where it gets hairy as it mentions publishing works or their fragments in educational textbooks, and so on yadda yadda, if they are specifically created and directly used at educational or research institutions for educational or research purposes. The problem here is that "directly used" almost certainly excludes anything like uploading a textbook on a web server.
The situation is interested. Jurs (the teacher) made a web site that he says is intended to let children freely study if they do not have money. It has some texts and it has audio lectures recorded by Jurs himself, as TFA says. The 4$ tag on the particular book surprises me - while indeed the salary levels are much lower in Latvia, it's actually cheaper than some textbooks were when I went to school, and that was a while ago. Checking online a bit, I see the average price could be in the 8-10$ range. But generally it's a known problem in Latvia with textbooks, poorer families are often unable to buy all the books and materials, while school libraries have very few copies, even though they are actually supposed to have enough.