These workers are considered under-educated due to lack of professional training.

under-educated 是由前缀 under-（表示"不足、低于"）和形容词 educated（"受过教育的"）组成的复合形容词。under- 表示程度不足，educated 表示"受过教育的"。 under-educated 合起来表示"受教育不足的"，指没有接受足够的教育或培训。