I thought the effects this episode were pretty good--it's nice to see all that forest around familiar monuments. The lighting gave Clara's face a soft warm glow. The fireflies reminded me of those I saw in evenings walking around the lake at Bled in Slovenia--they didn't seem alien to me. I thought the children were much less irritating than children in other stories--it's always tricky working with children.
I didn't think the teachers were very good at being teachers. They seem to forget their responsibilities and then every so often remember to do their job. I wonder what parents would sign the permission papers letting these two have their kids overnight in a museum.
I think the whole to-do about Clara lying to the Doctor about Danny and lying to Danny about the Doctor is overdone. This is the kind of artificial plotting you have in romantic comedies. X lies to Y and keeps lying, when telling the truth would clear up the whole misunderstanding. You see this on THE BIG BANG THEORY or in Adam Sandler movies.
It's not proof that Clara is a devil woman capable of crimes equal to the Master or that Clara is on the same moral/amoral footing as a Time Lord.
I don't like it when DOCTOR WHO takes something trivial, silly or mundane and tries to give it an unearned importance--often by having characters make speeches or using dramatic lighting or employing heavy music.
Also at the end when they cut away to Missy, yet again, I started to groan. They've gone once too often to the well with her and now it doesn't build suspense for me. I'm just tired of it. And that scene was so mechanical--a throwback to the old series, but not in a good way. It was as bad as if Missy had been watching the whole episode on a viewscreen and then cackled while she tented her fingers and gloated about her dastardly plans.