sentence in different form

[jchtse]

Hi,

I read the following sentence from a book:

"I have been teaching English as a foreign language to different age groups and at various levels of proficiency."

Is it possible for me to rephrase it as

"I have been teaching English as a foreign language to different age groups, which are at various levels of proficiency." ?

If yes, which form is better?

Thanks!

[svartnik]

I have been teaching English as a foreign language to different age groups and at various levels of proficiency.