I know a number of TAS teachers and students and parents. In general the level of education there is considered excellent. Many of the leavers there go on to top-end Uni’s in USA/Oz/UK etc etc.
The after-school and extracurricular activities/oppertunities are far far beyond those offered at most other schools on the island.
Teachers are incredibly well paid, but also can be under huge pressure/fired if the ‘wrong parent’ decides their child isn’t getting the results they have paid for.
In summary, its expensive but the oppertunities for those children who take them can be enormous compared to the local schools.