Toyota Celica Breaks Squeal?!?!?!? PLEASE HELP!!!!!!!!?

I have a 2000 Toyota Celica SX. Every time I break, the breaks make a loud squealing noise.

However, it only squeals when a certain amount of pressure is applied to the breaks. When I initially start to break there is no noise but as I apply more pressure it squeals then when I continue press harder it stops squealing.

I have gotten the breaks inspected by a mechanic when servicing the car and he said theres nothing wrong with them (disks and pads were in good shape). Please help!!!! Its quite embarrassing when you have to come to a squealing stop all the time.......

p.s. I notice quite a lot of break dust gathering on my front rims whilst the rear rims stay less dusty.