Something important in tag questions is the intonation: remember that if question tags are not real questions, the intonation does not go up at the end (as in questions), but, on the contrary, the intonation goes down. Watch this video and pay attention.
If you want to review tag questions go to this page for an explanation in English and Spanish.
Algo importante en las "preguntas coletilla" es la entonación: recordad que si la coletilla no es una pregunta, la entonación no tiene que ser ascendente (como en las preguntas) sino, por el contrario, descendente. Mirad este vídeo y prestad atención. Si queréis repasar el tema en esta página os lo explican en español y en inglés.
In one of our classes with Ryan we talked about "Stairway to Heaven" by Led Zeppelin. Here is the song with subtitles in English and Spanish.
I think this is one of the most beautiful songs you can listen to and at minute 6:52 you can enjoy one of the best guitar riff in the history of music. This happened back in 1973 (42 years ago!)
"Discuss the advantages and disadvantages of using mobile devices at school."
Even though you already work in a connected classroom, here is an interesting video about smart use of technology, for vocabulary's sake. And remember that it is a "discuss essay" so your arguments must be objective.
"The importance of being beautiful. Discuss."
Remember that, a "Discussion essay" is essentially a written debate where you are using your skill at reasoning, backed up by selected evidence to point out the advantages and disadvantages of the topic proposed. Reserve your personal opinion for the conclusion.