05/15/2009 AT 08:45 AM EDT
Looking like a lot of her classmates – giddy and irreverent, wearing a silly necklace of Blow-Pop lollipops strung together with curly gift ribbon – Bristol Palin stepped toward the stage in Wasilla Sports Complex Thursday night to receive her high school diploma, more a worried mom than a jubilant teen.
"Where's my baby?" Bristol mouthed, searching the two front rows where her family sat until she finally spotted son Tripp near the backstage door, where Bristol's Aunt Heather was feeding the infant a bottle. With a wave to the little one she alternately calls "Handsome" and "My Guy," Bristol crossed the stage – and crossed "graduate high school" off her to-do list.
"I knew it would be hard work, but I knew I was going to do it," Bristol, 18, tells PEOPLE.
Her mom, Alaska Gov. Sarah Palin, the former Republican vice-presidential nominee
, was not always so sure. Palin said in an interview that one of her first thoughts when Bristol announced her surprise pregnancy
last spring was, "Oh, there goes her education." "And that's why I'm so proud of her … really relieved," Palin says. "It's been a challenging and exciting year – her senior year – and I'm just so pleased that we are where we are today."
Bristol boasted a 3.497 G.P.A., regretting only that she was "point zero-zero-something" away from graduating with Honors. A budding activist
in the cause to prevent teen pregnancy, she says she hopes to go to an area college for a two-year business degree and then a job, possibly in real estate.