Have you stopped to consider that the lack of RSVP's may be due to the fact that the child hasn't passed the invitation on to Mom or Dad?
I'd love to be generous and bighearted and give the benefit of the doubt.......If it weren't for the fact that this happens to virtually
EVERYONE I know and when the dust settles, we discover the invitations did indeed make it home. It's just that the parents are too inconsiderate to take the 30-60 seconds to call or email to say, "Yes, Susie can attend," or "No, Susie cannot make it to the party." It's not just in my town. It's rampant everywhere and it is pathetic. True, some people may not actually know what RSVP means, but where I live almost everyone has a college degree and they do know what it means. As I told DH, if their husband's boss sent home an invitation, I bet they'd understand the meaning of RSVP fast enough.
Here's my most recent experience: DD had her party about a month ago and directories weren't out yet. Many parents aren't in the phone book and the school is so strict about privacy that they won't even give us a class roster. So DD gave me the names of all the girls (10) in her class and we sent invitations to them at school. The teacher confirmed that she put them in the backpacks. DD invited two additional girls from her school, who are not in her class. The teacher made sure they got the invitations. Long story short, getting the invitations home was NOT the problem.
I sent them nearly 2 weeks before the party and listed an RSVP deadline of the Tuesday before the party on Sunday. It clearly stated to respond to me, the mother, and gave my home phone number, cell phone number and email. As Tuesday neared, no RSVPs come in, even though DD said the girls were telling her they were coming. Considering that kids will say they're coming when their family has a trip planned, will invite your kid to a party that does not even exist, etc., I have learned to take a kid's word regarding parties with a grain of salt and that is why the RSVP said to respond to ME.
On Tuesday morning, I had to tell DD that if no one RSVPed, we needed to cancel that party and just do something else. She looked crushed. DH and I figured if someone showed up at the party place, gift in hand, who had not RSVPed, let them sit there and wonder when we were going to show up......

But on Tuesday night,
ONE parent called just under the deadline. The poor party person needed a head count and I had to tell her I had no clue how many were coming.
Between Wednesday (the day AFTER the deadline) and Saturday night (the night before the party) the RSVPs trickled in. Uhhhhh....The RSVP deadline is the LAST day to call, not the first day to call.

But at least they called. That's more than most people get.
I think DD scared the girls by telling them her mother was thinking of cancelling the party. They then lit a fire under their mothers.

Here was the final result:
Of the ten girls in her class, 8 eventually RSVPed that they were attending and they did show up. One never replied. One called to say she could not attend. I appreciated that.
Of the two girls who were not in her class, one called to accept and did show up. The other never called, but showed up an hour late as a total surprise. Thank goodness I had brought one extra goody bag.
Her mother never picked her up. Never. Ever. No joke. And yes, she knew the kid got there late and she confirmed a pick up time before she left. After the party had been over for well over an hour, we looked up her address and decided to drive her home, praying someone would be there. She said she didn't know ANY phone numbers, home or cell, because they had all recently been changed. I know the home number indeed had been changed. When we got to her house, the party had been over for about 75 minutes. DH took her to the door, it was unlocked and they walked right in.
No one noticed. At all. That's right. No one noticed the kid had come home because no one had yet realized she was "missing." Heaven knows WHEN they would have even thought to come get her. Poor kid.
So of the 12 girls invited, 10 showed up.....And to think, because of the lack of response, I dang near cancelled the party. I was afraid no one was coming. DD has always made friends easily and I wondered if she was losing her touch.

I swear, the year we took her to WDW for her birthday was more expensive, but less stressful than this party. No knowing until the last minute how many goody bags to bring, how much refreshments we'd need, how many supplies the party lady needed, or if only 1-2 girls would show up made me miserable. All because people couldn't call or email on time, which would have taken seconds. And let's not forget.....I'm one of the more fortunate moms, in that I at least got replies at some point.
Seriously, I think I'm done with parties like this.