can somebody explain the meaning of threshold in this sentence?

Hello,
For my master thesis, I am reading an empirical study on multilingualism. Can somebody please explain the meaning of the word threshold in the following sentence?

The multilingual teachers outperformed the bilingual ones in High Awareness answers. However, the distribution of the answers could not be explained solely by the bilingualism/ multilingualism factor. It turned out that the multilingual teachers who rated the level of their L3-Ln languages as at least intermediate (B1+) gave significantly more High Awareness answers to the questionnaire than those teachers who rated their L3-Ln as elementary (A1/A2). The data suggest that teachers should preferably be multilingual in order to be aware of the benefits of plurilingualism, but the threshold for the L3 knowledge seems to oscillate around the intermediate level (B1+).

Thanks for your reply.

Regards,
Kati