What happened was that in USA, when they arrived, they were a year ahead of most of the curses. They have to sit and just listen. They weren't allowed the finish a year early because the way courses are teached here didn't follow the same scheme than in Argentina and Europe. So for a few that were in synchrony they just stay and finish the high school based on age, more than in knowledge.
We had several issues with the French teacher, they started to correct her. To the point they need to be removed. Similar issues we had with Math, Geography, etc.
For them was all fun, they couldn't belive the amount of free time, as students, they had here in USA.
Just be careful. In Argentina we all went to bilingual private schools. State school are a differentstory. In Europe they went to the state school. They have compulsory to learn 3 languages. In Argentina we sent them for 1 year to a private French professor in preparation for Belguim. At our arrival to Belgium they attended a state school in Brussels, where they had to learn Dutch, Latin, French and English (Brussels has French and Dutch as official languages). They only managed well English. That was too much. 6 months later they started in a state school in Waterloo (the town of the famous battle. The school was 1 Km from that historic place). Waterloo is within the French speaking region of Belgium. So the school language was French, and then they had English and Spanish. Now it was a piece of cake for them. They were 11-12 YO at that time. 2.5 years later they landed in USA. School was a party for them here. They were soooooo happy
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Cheers
Daniel