Can boys and girls play together in junior touch?

Yes, in some competitions. Touch Football Australia's Junior FAQ says boys and girls can play together in some mixed competitions, though junior competitions are often specified as boys or girls only.

The National Junior Development Framework explains that touch is a minimum contact sport, so players are not put in physical danger when competing with larger players. It also says most junior competitions are single gender, and that affiliates are encouraged to test and trial what works best for them.

Under the 8th Edition Playing Rules, in a mixed gender competition a team can have at most three males on the field, with at least one male and one female.

Sources: touchfootball.com.au/play/junior-faq, TFA National Junior Development Framework (version 2, January 2013) and TFA Playing Rules 8th Edition, rule 5.4.