Hot answers tagged syntax
Yes, 次第に modifies 少なくなり in that sentence, nothing else. One cannot say 次第に登校する in the first place anyway because "going to school = 登校する" is not something one can do "little by little = 次第に". 次第に少なくなる, however, is a natural-sounding phrase because the number of something (students in this case) CAN decrease little by little. You are also correct in ...
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