Learn Russian: Мы редко нанимаем студентов, хотя они быстро учатся. - We rarely hire students, although they learn quickly.

Yes! In Russian, you must always put a comma before conjunctions that start a new clause (a part of a sentence with its own subject and verb). You will do this before words like хотя (although), что (that), and потому что (because).

Why is the word for students spelled студентов here instead of студенты?

Because the students are the direct object of the verb нанимаем (we hire), so the word needs to be in the accusative case. For living things (animate nouns) in the plural, the accusative case takes the exact same ending as the genitive case. Since студент is a masculine noun ending in a consonant, it gets the -ов ending.

Why does the sentence use the reflexive verb учатся instead of учат or изучают?

Учат and изучают usually need a direct object—you have to state exactly what is being learned (like a language or a subject). Here, we are just talking about the general ability to learn. For the general action of learning or studying without mentioning a specific topic, Russian uses the reflexive verb учиться (they learn = они учатся).

Does the adverb быстро (quickly) have to go before the verb учатся?