You can prepare your subcorpus of MERLIN texts (e.g., sorted according to CEFR ratings) and bring it to your language classroom. Your learners can discuss strengths and weaknesses of written productions.
Make your students understand their own L2 competence with relation to CEFR levels:
Your learners can use the MERLIN rating grid for self-evaluation, they can do one or more MERLIN tasks, and they can compare their performances to the subcorpus you prepared. Thus, they can more easily understand where they are in their language learning process as well. This might be more appropriate for learners from B1.
To find written test of learners that performed on a specific CEFR-level:
Bring the platform to the classroom:
You can also let your (advanced) students look for language phenomena in the MERLIN corpus by themselves in order to familiarize them with the technology and enhance their autonomy in language learning. They could do peer-group error analyses of MERLIN samples, but also of texts of their own. You could have them compare MERLIN data with a native speaker corpus to illustrate differences in language use.