Allow and Deny Blocks
Allow and deny blocks can be used to create restricted building areas or areas where users can build.
They are obtained by selecting from the inventory when in creative mode or by typing the following commands into the chat:
Allow and deny blocks are particularly useful when you want to specify an area for students to build on or an area they cannot modify.
You may also decide to turn on the immutable world option in the settings, then create an allow block area for students to build. This means your entire world except the allow block area cannot be modified or destroyed.
If you still want your students to build on a particular surface, such as grass, simply place the allow block underneath. The allow block allows an infinite distance above the block, but does not cover the area below the block.
Students with world builder status can place and remove these blocks.