So many similarities:
--age 1 numbers and letters
--age 2 learning to read, math, solar system, time
--age 3 geography (state & country borders, shapes, capitals, landmarks, flags), periodic table
--age 4 games games games (monopoly, fits, sims, logic games, parcheesi, creating own board games), drawing maps & other objects from life, building angry bird setups, swimming, anatomy, managing our days from the perspective of dates, location, time & money