Ski schools don't do avalanche training. It needs to be done by mountain guides.

Check out Eiselin Sport or Rock and Powder, I've done courses with both of them in the past. Most of the mountain guides offices in the major resorts will offer avalanche courses too.

Take the fatalities in context too, riding just beside the piste near the lifts first two lifts in hoch-ybrig is probably safe the vast majority of the time. The fatalities happened on the weglosen abfahrt which is off piste next to where the black piste goes down to the valley. This is a north facing steep slope that gets a lot of snow and wind depositon. Prime avalanche territory.

All of the first off piste rides I did were in Hoch-ybrig but up in the ski area where it gets very tracked over within hours of a snow fall. In general the area is very flat up there and it is a pretty good place for getting to grips with off piste.