You assume that the anecdotal 1/3 are receiving tutoring because they are struggling. 

The last of my three children graduated from public school (French immersion) last year. Many in their network were receiving tutoring to get 90s rather than 70s or 80s. Competition in a winner-take-all world  rather than inability of the education system. 

Certainly there is always room for improvement in education and encountered more than a few teachers would be be better off selling real estate. However, each managed to achieve well scholastically without the assistance of tutors. One graduated top of the class, the other two within the top 1-3%. Good sleep behaviour, healthy diet, active lifestyle, and encouraging support (along with the occasional hard word) from Dad and Mom was more than enough to overcome the absence of tutors or weak teachers. And hey, maybe good genetics accounts for something too.  :-)

Too easy to blame the education system.