You guys are so awesome!!. Thanks for sharing your knowledge and information. I will go through every option that you all suggested. 

Thanks for your response. I did read that discussion. But, I was not sure how to train my son on the Peg System.  Do you have any info about that? Or I hope Chris reads this thread and can explain.

Hello, I learnt Abacus 3 years back and have been teaching my son. I started teaching my son about 2 years back when he was 9. He can currently do 5 digits(addition/subtraction), 3*2 multiplication and 4by2 division using abacus. On Mental Math he can do 2 and 3 digit 10 rows (with 70% accuracy), 4*1 multiplication and 4by1 division.  He practices 20 minutes atleast 5 days a week.

My questions:
1. What do you think about my son's progress?
2. I saw a video where the girl does 10 digits 10 rows in about a minute. I feel that she is doing 2 or 3 columns at a time and remembers the numbers. Can you tell me how she is able to    remember the final answer and at the same time keep calculating. I read in a forum that she is using PEG system. Can you explain what peg system is and how I can train my son?
3. Many schools say that they train the students to visualize. Is there any special training as such? I asked my son and imagine the abacus and calculate and he was able to do it.

Thanks in advance for taking the time to reply.