Dov- because you get good hours, good benefits, summers off- ideal for working mothers, especially. No job is perfect, and very few will automatically grant you off for Jewish holidays, unless you work for a frum boss.
Besides, small children usually use a lot less nivul peh, and show a lot less pritzus and immorality than you might find in an office/business situation with adults. Yes, these required topics would prove problematic, but I doubt these are taught at every grade level. Nor would it apply to paraprofessionals, therapists etc who work for the board of ed but not as teachers. The non-Jewish kids would love to be taught by frum Jews as long as they are good teachers who care about their students.
And it is not at all hypocritical- And plenty of teachers don’t send their kids to the schools they teach in. How many white teachers in inner city schools would send their kids there? For that matter, how many upper-middle class educated people would send their kids to public school at all (specifically, NYC, other areas are better). Even in the frum schools- are there no MO teachers in yeshivish schools, or chasidish rebbes in litvish chadarim or hareidi teachers in MO schools?