You asked a clarifying question. The clients are the parents, persons born abroad and usually educated abroad through their undergraduate degrees. They arrived to the United States after being born abroad, so they are first-generation immigrants (as is my wife). The students are elementary-age pupils, typically born in the United States, whose parents seek supplementary mathematics lessons for the children when they observe how weak the mathematics instruction is even in schools in the United States that are in desirable school districts in one of the states of the United States with the highest level of academic achievement. There is a lot of "ceiling" above the best curriculum provided to bright students in United States schools that can only be reached with supplemental programs such as the one I have helped organize here (which is based on a program that originated in Michigan, among the Indo-American community there). Native-born American parents who are alumni of MIT and a variety of foreign-born parents have all recommended my program to their friends from various countries.

P.S. I used to use a book that was written in Russian (by Estonian authors before the break-up of the Soviet Union) and then translated into English as one of my course textbooks.

http://www.perpendicularpress.com/math6.html

The Russian mathematics textbooks are often very good indeed, and much more clear and more challenging than typical textbooks in the United States. You might find it interesting to read a link I learned about from another HN participant, "Word Problems in Russia and America," by Andrei Toom,

http://www.de.ufpe.br/~toom/travel/sweden05/WP-SWEDEN-NEW.pd...

which is full of interesting information about the differences in approach between mathematics lessons in Russia and mathematics lessons in most United States schools. The contrast between schools in China and the United States

http://www.ams.org/notices/199908/rev-howe.pdf

http://www.math.wisc.edu/~askey/ask-gian.pdf

or between those in Singapore and the United States

http://www.merga.net.au/documents/RP182006.pdf

are also food for thought.

I'm glad you liked it. I was lucky to take a statistics course with Prof. Toom at undergrad.