The video is impressive, but he isn't playing against anyone.
The part where he's playing for his school? Definitely. That's about the same level as when he's training against the chairs. Maybe even easier.
High-school ball in Australia isn't like high-school ball in America, not only is basketball a secondary sport here (Australian Football or Rugby is the top winter sport, depending on which state you're in), it isn't even the top level of junior basketball, as each state runs its own junior league which would be closer in standard to high-school ball. However, the best junior basketballers in Australia, like Dante, get scholarships to the Australian Institute of Sport (AIS) where they run an intensive training program. While at the AIS they still go to high school as normal, and the closest high school to the AIS is Lake Ginninderra (hence "Lakers"), so most of the AIS players go there. Basically his high-school team was an All-Star line-up against regular schools where basketball isn't even the #1 sport. No surprise his team won.
The AIS program, though, features intensive training, comparable to college-level, and with an emphasis on fundamentals, and games against competent opposition. The training session in the vid is an AIS session. The AIS program was started in the late '70s to produce basketballers that could compete against the college-level USA players then playing in the Olympics, and its aim is still to produce Olympic-standard basketballers. Almost every Aussie that has played in the NBA (including Longley, Bogut, Mills, Baynes, Dellavedova and Andersen) is an AIS Graduate.
From the AIS website, about their program:
Both the Basketball Australia AIS women’s and men’s programs train six days a week, 1-3 times a day. Training includes team practice, “individuals”, where players will usually work on specific skill development and technical aspects of their game, as well as strength and conditioning work in the gym. Team practices usually last between 1-2 hours and like games, involve a lot of high intensity efforts interspersed with variable amounts of recovery.
Both the men’s and women’s program go on 1-2 overseas trips a year to play against under-age national teams or semi-professional club sides. The AIS also hosts overseas touring teams multiple times each year. Most of the athletes will also be involved in the annual week-long under-age National Championships, while many will also compete in the U/19 World Championships, which are held every two years.
Dante is a member of the junior national team, and there are some brief snippets of a game from the U19 World Championships in there. Dante is also part of the senior national team program, and he was the youngest player ever to be included in the squad, although his on-court appearances have been brief.
So basically, Dante has been participating in a college-level program for two years, and has played against the best players in the word in his age group, yet this video focuses on him playing in what is a glorified pick-up game.