If you really want to know statistical information about mass public school systems just look at DESE stats. DESE employs a fair amount and they look at this information constantly.
2014-15 Per Pupil Expenditures Statewide Report
To note costs per pupil can be high on a number of factors. One is just the economy of scale. Fewer students means they have to spend more to justify vendor costs of operations. In addition grants are a significant factor. Vocational schools tend to always cost more due to the equipment but with time that drops.