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Open-ended work with real materials18–21 months

Wooden Unit Blocks

Plain hardwood blocks in mathematically proportional sizes, unpainted, with no pictures or letters on them.

By the Educate With Play editorsReviewed How we work
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Offer it around
18–21 months
Montessori principle
Open-ended work with real materials
What you may see
  • Stacks four or more blocks
  • Places blocks in a horizontal line
  • Builds an enclosure or a bridge

Unit blocks are cut so that two of one size equal one of the next — halves, doubles, quarters, all consistent. A toddler stacking them is not being taught fractions, but they are handling a system in which the relationships hold true every time, and the hands learn that before the mind can articulate it. Blocks with letters and pictures printed on them cannot do this, because the print draws attention to the surface rather than the form.

At eighteen months the work is mostly vertical: stack, admire, demolish, repeat. Knocking the tower down is not destruction, it is the most interesting part — it is the only way to find out how the structure behaves. By two, the same blocks start being laid horizontally, enclosed into rough squares, and bridged. Each of those is a distinct construction idea arrived at independently.

The weight is the thing to insist on. Hardwood blocks have enough mass to stay where they are put, so a tower stands and a child gets to see their own success. Light pine blocks shift as the next one lands, which produces a lot of collapsed towers and a fairly quick loss of interest.

What to look for

  • Hardwood with real weight to it
  • Plain, unpainted, no printed letters or pictures
  • Consistent proportional sizing
  • A storage tray, so tidying up is part of the work

Not this

Alphabet blocks and printed picture blocks — the decoration works against what the material is for.

Safety

Keep towers below the child's own height and build on the floor rather than on a table.

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Also for 1–2 years

The rest of this stage