Translation:The teacher is sitting across from the children.
Thanks very much for the explanation.
When thinking in German, I'm inevitably influenced by Dutch, where the literally equivalent preposition is tegenover and it's used only as such (e.g. Ze wonen tegenover het Stadhuis and De lerares zit tegenover de kinderen).
This is one of those areas where German subtly differs. Given that German has a huge amount in common with Dutch, I find it easiest to learn by mostly thinking about it as a set of differences.