is it possible to have 30 days China Tourist visa extended in China?

I am a Nigerian who was given a 30 day Tourist visa to China. I was wondering if it is possible to have this visa extended in China because I am there to take language courses for 8-12 weeks (that longer than 30 days but not long enough to apply for a student visa). I would be exceedingly grateful if you can address my inquiry, it would be very helpful and prepare me for my trip to China.

Thanks again! :)