Here's one option: If we have a single data frame, we can do, for example, iris %>% slice(-(1:50)) or iris[-(1:50), ], to remove the first 50 rows. For data frames in a list, we can use map() to apply the same approach to every data frame in the list.
library(tidyverse)
list.school.data = map(list.school.data, ~ .x %>% slice(-(1:50))
or
list.school.data = map(list.school.data, ~ .x[-(1:50), ])
In base R, a similar approach would use lapply:
list.school.data = lapply(list.school.data, function(x) x[-(1:50), ])