I know they are taking nothing home, and emails sent to teachers are answered during the next school day. Like tokens at my job, it is easy to claim they are working when it is impossible to verify/quantify the work.
Those paras who do the grunt-work average $10-$15/hour [and they must have bachelor's degrees], and freely admit they accept the crappy pay so they can be home with their kids during the summer and shortly after the school day ends. [For many paras the most important part of their compensation is healthcare, not cash on the barrelhead.]