Mastery of combat, math, and most things is predicated on proper understanding of fundamentals before increasing complexity.
Brand new people will come into a gym and be taught arm bars, triangles, and other attacks before they know how to get out of pins or move from position to position properly with economy of movement.
Children who still use their fingers (even if quickly) should not move on to harder operations. The inability to multiply quickly makes fractions and algebra a nightmare for children. Trying to read chapter books when children are still sounding out words reduces reading comprehension to almost nothing.
For beginners/children this cannot be done in a group setting. An instructor has to be available to monitor the proper understanding of these things so that time is not wasted reviewing where kids have mastered a chunk of fundamental knowledge or worse, moved on to a more complex procedure when still struggling with basics.
