核心问题
〔Carver's efforts began to show results. But not enough farmers could visit Tuskegee to see for themselves how these new crops and methods were working.〕So Carver decided that the school must go to the farmers. (American Men of Science and Invention, p. 78)
[原译]〔卡弗的努力初见成效。但并不是很多的农民都能亲自来塔斯奇基参观这些新作物与耕作方法。〕因此卡弗决定应当走出学校到农民当中去。（中译本） 译文中的“决定应当”似乎不符合汉语习惯。
词典解答
decide 还有一个我国出版的许多英汉辞典未收入的词义：“肯定”“断定”“认为”。例如下面各句中的 decide 都不能译为“决定”。
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We have decided that it's no use to worry. (Galsworthy) 我们认为忧愁是没有用的。
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Her mother, he decided, was an invalid. (Mansfield) 他断定她的母亲是个病人。
因此你所问的句子可改译如下：
[试译]……卡弗认为他必须把课堂搬到农民当中去。
(参见 should )