Table 2. Number of studies (out of 143) that report on the different demographic categories of K-12 participants.

Demographic category	Number of studies	Percentage
Age/grade	134	94%
Gender	92	64%
Race/ethnic background	46	32%
Socio-economic status	28	20%
Disabilities	6	4%
Location	96	67%
Prior experience	52	37%