Kept outside in moist/rainy conditions the rotors get a thin layer of surface rust which will growl, not screech, the first few stops. Cheap pads usually don't screech, because they have softer surfaces and wear out quicker
Often a high pitched screeching is the result of two mirrored surfaces in contact. Sounds like pads did not break-in in properly, could be too many hard stops and/or riding brake heat glazed the pads and they screech when in contact with the rotor.
Pulling and scuffing the pads and rotor surfaces will at least provide a temporary, or possibly permanent fix depending on pad surface condition. If not permanent ....new pads and skinning the rotors.
Current Chevys -'19 Silverado RST;'18 Malibu LT Redline;'18 Traverse Premier Redline<br /><br />Previous Chevys:16 Silverado LT;16 Malibu LT2;'17 Impala;'16 MalibuLT;'15 Camaro LS;'15 Traverse; '13,'12 and '07 Avalanche LTs; '11 Tahoe LT; '13 &'11 Malibu LTs; '08 Trailblazer;'06 Colorado WT..... Chrysler era.....'80 Citation;'75 Impala;'72 Chevelle;'69 Camaro R/T;'65 Impala SS;'62 Nova