Personally, I have always hated the "whole class" idea! It's ridiculous to think that 20 or 25 kids just love to hang out, and it's such a burden on parents to have so many parties throughout the year. And 25 guests looks, to most parents, like a "gift grab" - guests bring a gift which the birthday child doesn't open in front of them, and then they wait 3 weeks for the 25 thank you notes to get written (if they ever do). Then it starts over for the next birthday the following week. It gets old.
A preschool class of 6? Maybe invite them all. But by 10, kids need to learn to make choices, evaluate friendships and, quite frankly, learn to handle not being invited to everything. It also doesn't hurt them to learn a few skills, like not flaunting an invite they received in front of everyone else.
We had the "year rule" - at 5, our son invited 5 kids. At 8, he invited 8 kids. By 10, he wanted to do something more expensive than a home party, so we limited the guest list even more. If he wanted movie/lunch or a laser tag thing, he invited just a handful.
Don't be held hostage by the "left out" thing - the fact is, people make choices all the time and someone is left out all the time. If she had a class of 13 and wanted to invite 12 and not the 1 remaining kid, I'd say not. But that's not the story here - she's growing up and becoming more discerning. I say to invite the kids she likes, be instructed not to talk about the party at school, learn to open gifts at the party and say a proper "thank you and I love it" while the guests learn the skill of enjoying this without a gift being for them, and let your daughter learn to write a decent thank you note - no emails notes. (Our son was told to either write a thank you note for the gift, or give the gift back with a note about why he didn't want it! Of course he wouldn't do the latter and we wouldn't permit it, but you get the idea - there's a note being written no matter what, and you can't play with the gift or spend the gift card until the thank you is written. Social skills!
Please, buck the trend in your area and stop with the big parties. The other parents and kids will thank you for it!
ETA: Please do not send the invitations to the school! That puts the teacher in charge of your daughter's social arrangements. It also makes the teacher an agent of including some and excluding others. Neither of these is the teacher's job. When I was teaching in 2 different schools, this was a huge no-no!! Please don't take advantage of the teacher this way. Send your daughter with a small list of the kids she likes and have her discreetly get addresses. At 10, kids know how to write their addresses. Then mail real invites with real RSVPs. If your daughter cannot get the info, then she's not old enough to have a party of this size.