Please help.
The following sentences confuse me:

In these circumstances there are two guiding principles which should influence your decisions: that language teaching is only an aid to language learning, and that it is those things which help the students to improve which are of particular importance; and secondly that language is first and foremost communication.

Could you please explain what the phrase 'those things' refers to?

Thanks for your help.

Given the subject of the sentence, it is quite ironic how poorly written it is.

There is no antecedent of those things further back in the sentence.

Read the text below and then re-read the original.

...the things that help the students improve are important...

I hope that helps.