Ex; What happened when Vinegar was added to baking soda.
Typical Anwser: There was fizz
Better Anwser: When Vinegar is added to baking soda there is a chemical reaction that causes a fizz which makes a gas. The fizz made the contents of the glass overflow. After a minute the fizz stopped...
I don't know what's expected of children's lab reports, but on general principles I would want the observations clearly separated from the theorising about might be causing them. E.g.
When I added the vinegar to the baking soda I heard a fizzing noise and I saw a white foam rise up the glass. The foam overflowed the glass. I could also smell the vinegar. After a minute the fizzing noise subsided and the level of foam fell.
I deduce that a chemical reaction took place which produced a gas. 
