I received this letter:

Comment: Hi, My son is going into ninth grade and is taking Lingua Latina with you. He really enjoys it but also wants to learn other languages. We didn’t do a good job of passing on our Spanish to him and he wants to learn it before he graduates but he also wants to learn other languages. I am not sure what the best way is. I would really like him to finish lingua latina before doing another formal study but I’m not sure he will finish in two years. Ideally, he would finish lingua latina in the ninth grade and move on to other languages for tenth through twelfth. He recently started Spanish on DuoLingo and I encourage him to continue with that. I am also going to be doing some conversational Spanish with him and the little ones so he can grow. He understands well but speaking is difficult. I really think he is capable of learning both languages at once because he already understands so much Spanish but I don’t want to overwhelm his academic load next year. I am thinking about removing something to replace it with Spanish but its a tough choice. What are your suggestions? What is the best way to keep up Latin when Lingua Latina is finished? I would hate to see him forget the Latin he has learned. Thanks!
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Here is my reply:
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You can definitely learn more than one language at once.  Though it’s a bit ridiculous, I am currently working on seven.  The thought of this does not bother me.  I have seen it done, and know it can be done.  Europeans and Africans verify this truth every time I meet them.  It is not uncommon for them to speak four or five languages.
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If you don’t want your son to lose the Latin and that he has learned, continue on with it.  Yours is a good plan.  Jump from Latin to Spanish, or another modern language.
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However, I do think it’s a tragedy when students spend three or four or five years studying Latin and, in the end, are unable to speak it.  They have no one to talk to, and no country to visit.
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Much better to learn Spanish, French, or Italian fluently and then come back to Latin.  Latin isn’t going anywhere.  It will be there when he comes back.  I didn’t start learning Latin until I was 23.  According to his autobiography, Benjamin Franklin didn’t start learning Latin until he was 40.