I think we have all gone through this: deep breath and realization that I have my hands full. I think it helps us get over denial.
I stopped looking at milestones a long time ago when DD had completed everything for 3 month olds by the time she was at the most 2 weeks old.
As for your question, it depends on your area and the PS. Most kids in my district definitely know their numbers by preschool (age 4) and by kindergarten all know counting up to 10. I first thought we had a lot of gifted kids in our area but I.have come to realize most are high achievers (which is different). High middle class families with time and ability to give their children an early start. Even though our local kindergarten is more advanced than others around our district it still would never be enough for my DD who was counting before age 1 and knew her ABCs before age 9 months. This is why we chose a more academic route where at age 4 they are doing 1 st grade material but all is taught in Spanish and even this is.not enough of an advancement for her.