Though more colloquial in tone, it is not incorrect to use "better" as a verb synonymous with "improve" (I double-checked in "Use the Right Word" just to make sure).

And, I would only hope that the teacher would uproot mistakes . I would be more concerned if s/he made them ingrained or planted (if you want to stay with the botanical vocabulary) them in the children´s minds.

..we are learning all the time and it is fascinating.

 None of the languages is difficult enough if you have so called language aptitude and do you really think English is the hardest of them to learn?

And as far as kids are concerned ,in my opinion the best of teachers should teach them.Young learners absorb info so quickly and if the teacher is pseudo´teacher´may do more harm to them than good.He or she may only root mistakes and make their learning more difficult in the future.

Anyway

for games and other resources look at

www.englishtips.org

Russian site that provides all books,dictionaries,films,software,games,ect...

English version available,to download you must register

one more thing,future teacher of English

we say

to improve English not to better...no personal offence..just a thought

 Actually it is not wrong to say:

I will better /improve my English by attending classes

or

If I attend classes I will better / improve my English

So either is fine.  I think to use  "better" in this way is may a little old fashioned