I prefer individual lessons(,) where your teacher and you can be more concentrated/focused and work on specific topics

Question

1. Which word fits this sentence better?

I prefer individual lessons(,) where your teacher and you can be more concentrated/focused and work on specific topics.

Cambridge Dictionary suggests that 'concentrated' might mean 'using a lot of effort to succeed at one particular thing':

https://dictionary.cambridge.org/ru/%D1%81%D0%BB%D0%BE%D0%B2%D0%B0%D1%80%D1%8C/%D0%B0%D0%BD%D0%B3%D0%BB%D0%B8%D0%B9%D1%81%D0%BA%D0%B8%D0%B9/concentrated

However, it somehow sounds as if I'm talking about juice. :) Can people be 'concentrated'?

2. Is the comma necessary in the sentence? I think it's a non-restrictive relative clause cause the information it introduces is not essential. Am I right?

Answer 1

I prefer individual lessons(,) where your teacher and you can be more concentrated/focused and work on specific topics.

The term focused is more appropriate. Also, as the relative clause is non-essential, comma is used.

I suggest changing the relative pronoun where to during which as the direct object, individual lessons, is more a time duration than a place.

I prefer individual lessons, [during which] your teacher and you can be more focused and work on specific topics.

Guide on the use of the form which + prepositions is shown below.

https://dictionary.cambridge.org/grammar/british-grammar/relative-pronouns

We can use which as the complement of a preposition:

Close by, in the churchyard, is the famous Rudston stone, from which the village takes its name. (which refers to the famous Rudston stone and is the complement of from).