Flying domestic from Shanghai to Beijing? Or Train?

Trying to determine which way would be more economical.
I will be arriving in Shanghai with 2 international weight bags - I will be teaching English in Beijing for 3 weeks so I will be carrying many school supplies.
Can I ride the train with two large bags? Will my bags fit in the train car with me since I know that there are no freight cars for the high speed trains.
OR should I get a flight on China Eastern and pay the overage? How would I calculate the overage fee?