Hey, They are both correct. "Each of them" + verb at singular instead of "each of them were" because the subject with which the verb has agreement is "each" (singular form), and not "them". As for the Genitive of "class" you may use either "class`"/ "class`s " (both are correct) or "of the class" , depending on the context ( you can have partitival genitive : "a member of the class " ) Cheers, Diana.
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