Can i go to Summer school a week late?

Can i go to summer school a week late? I ended the semester with terrible grades and i tought that im going to have summer school so i waited for the mail to come with my schedule because before i got a mail that said that the schedules are distributed by mail ,but it did not come so i did not go. And today (week after summer school beginning) my friend told me that he also did not get a mail ,but he went to pick something up the first day of summer school and they told him that he has summer school even tho he did not get the mail. What should i do??? At my school they said that once you miss only 3 summer school days you fail , im in highschool