Teaching shorashim: Why bother?

So many people come to my blog after googling "teaching shorashim." Obviously this is a topic of great interest.

Knowing hebrew roots (shorashim) is the foundation for being interested in learning independently.   In other words, the more basic hebrew vocabulary a student knows, the more likely he is to experiment and try to learn more pesukim on his own.  According to Jeanne Gunther, Students learn independently when they can understand 94% of the text. Instruction takes place when they understand 90-94% of the text. Frustration comes when they know less than 90% of the text. The goal is to have the students at the 90-94% before they open the chumash and become frustrated.

I have taught high school and some students didn't know basic shorashim or common nouns. How could they hope to learn on their intellectual level when they are so hampered by their inadequate vocabulary knowledge?

I began teaching third grade with a desire to help the high school students who gave up before entering my class.  In the early elementary grades, learning is exciting and so much can be taught in this short window of time.

My system for teaching shorashim is based on the fact that
 b) there are  different modalities of learning 
c) keeping it fun keeps students motivated
d) pre-learning vocabulary gives students a sense of accomplishment and control
e) It is important for students to have the resources so they can learn independently if they choose.
f) Students haven't learned enough to differentiate between "common" vocabulary words and "rare" vocabulary words. If the words are taught in a memorable way, some students will remember most of them forever. All students will remember a lot of them forever especially if there is adequate review.
g) Every student should be in the 90-94% window before we learn a pasuk.