Little posted here addresses the issue. I'm a long-term educator, but not in the EU. Before bad health forced me into retirement, I was a school administrator. In American public schools there is little place for religion. Teaching religion in public schools runs up against the constitution. But that doesn't mean educators are insensitive to religious issues. Ideally, teachers should keep their personal feelings out of religious discussions. They will arise. During my tenure I suspended or fired three teachers for abusing students over their religious choices.
If you're pursuing this topic you will want to familiarize yourself with Witness doctrine and practice. Read their literature, attend a meeting or two. But you will want an outside view too. I recommend Zoe Knox's new book: Jehovah's Witnesses and the Secular World. This is a largely accurate consideration of Witness culture that discusses its conflicts with the state and society. I also recommend George Chryssides' Jehovah's Witnesses: Continuity and Change. Both books have some errors, as do most books on Witnesses, but they are largely neutral. And neither author lies to you. I should tell you that Zoe says nice things about my book in hers. But I'm not recommending her book to you because of that. I should tell you that I am on friendly terms with both authors, but it is a professional, not a social relationship.
Not all Witness children have fully adopted that faith. Some will leave it as they approach adulthood. Some are fully committed from a very early age. Nevertheless, they and their beliefs should be treated with respect, especially by teachers. Some Witness practices put children in a sometimes uncomfortable spotlight. A teacher's duty is to mitigate that. Accommodate difference in the gentlest and most sensitive way possible.
In a class that examines historical roots, point out that Witness theology rests within Christian history, just not withing 'orthodox' history. At one point elements of Witness theology dominated Europe. An even handed teacher will not present religions as true or false, but just present matters as they are. This requires a depth of research not characteristic of most lower-grades teachers. And there are few to no texts and guides that fill the gap. A religion teacher should be an adept and committed educator.
Some Witness children are very open and adept speakers. For some years I taught Gifted and Talented students. An uncharacteristically high percentage came from Witness families. They were articulate and willing to prompt class discussions. Give Witness students an opportunity to speak if they want to. This should be voluntary, not forced.
If you want more from me, say so here or PM me.