Question: what grade is 12 years old in usa
[{'answer': 'Seventh grade', 'provenance': [{'wikipedia_id': '1065956', 'title': 'Seventh grade', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 13, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]