How is it hypocritical you ask. Let me reference the situation in my area's public school system as example: When our local lawmakers invoke a new tax or raise the current ones, some of this money is inevitably spent toward what they term "school renovations and maintenance". But in fact we see very little funding go toward things like replacing old buses, salt for the school bus routes, replacing basic school room necessities, repairing falling structures, offering sanitary napkins in the girls restrooms and so forth. The last tax increase has brought us brand new sports uniforms, additons to the HS football stadium, materials aimed at social awareness projects (LGBT and Islamic awareness and such ) and an eleven percent teacher salary raise. Now while I don't begrudge teachers being paid a living wage (there are many teachers in my own family! ), in this region a single teacher pulls in an average yearly earning of 42K (along with benefits and retirement plan), while the average income of two parents with school-age children is a combined 34K.
I wouldn't send a child of mine to a religious charter school (mine have all graduated now and if I had to do it all over again I'd home school). I am not Christian nor are many of my friends. But none of us are comfortable learning that children in the area are being told in the classroom that to like our current President is wrong and that America has never been great, or that they are being taught a complex course in sex ed before they are even old enough to be interested in sex. There are several other issues in play, too, though it'd take too much space here to address.
So I understand why parents are fed up with the public educational system, particularly with teachers unions. They are the first ones to demand a piece of the tax pie. What annoys parents more than this is that the modern teaching establishment is so heavily invested in undermining of parental intake in what is taught to our kids. This likely is, I feel, the reason many have turned to homeschooling and charter schools. So when public school teachers and unions argue that funding for charter schools takes away from their deserved pieces of the pie it does smack of hypocrisy. Apparently the charter schools are providing something they aren't willing to give in the public school arena, and this is respect for parental discretion and rights.