Vivinavi

My child is still very young so it will be a while before he/she attends, but I am looking into it. I think the most famous Japanese language school is Rainbow Gakuen, but what is the difference between Rainbow and Sakura Japanese Language Preschool that I found while researching ？ I know that Sakura is from 2 years and 10 months to about 5 years old ？ and Rainbow has a kindergarten (from what age, I'm not sure) to middle school.
Either way, these are the only ones that I know of. In any case, these are Japanese language supplementary schools, not like pre-schools where you leave your child ？ I wonder if most people who send their children to these schools send them to both pre-schools and Japanese language schools ？ My old boss's child used to say Rainbow only on Saturday I think I read somewhere that if a child cannot speak Japanese to some extent, he/she cannot even enroll in Rainbow. Is it difficult to get in ？
Various questions themselves are vague, but if you know anything about these facilities, please let me know.