[susan53]

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If you google for frequency, you get

"English class" - 1,240,000 hits
"English lesson" - 665,000 hits

I think it might be a UK/US thing. I've just repeated your search and obviously got more or less the same numbers - ie a ratio of class 2: 1 lesson.

But I then did it again restricting the search to UK websites - and therefore presumably British English - only and got :

English class 104,000
English lesson 95,000

ie a (very approximately) ratio of 7:6

So class still wins, but as I suspected, there's a big difference in frequency of use between the UK and "the rest of the world".
Does Google have a US site where you can restrict to US websites only? Or someone might like to try Australia and other English speaking countries and see what happens.