Gramatically they are correct, although adding the at the beginning would make them sound better.
In the first sentence, the teacher spoke to the parents; in the second one the concerns are addressed.
Are the following sentences correct, gramatically? If yes, is there any difference in meaning between them?
1. Teacher spoke to the concerned parents
2. Teacher spoke to the parents concerned
2 answers
Where you place the adjective "concerned" makes a difference. In sentence #1 it is clear the parents were concerned. In #2 it could be the teacher was concerned. Go with Anonymous' suggestion of beginning #1 with "The" but I would not use sentence #2.
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