Utah schools grew by a whopping 8,744 students last year — the single largest annual growth spurt since 1991, the State Office of Education reports.

And that's just the initial droplets of a coming growth wave of 145,000 new students in the next decade, state finance and budgeting special- ist Patty Murphy said Friday. Next fall, she projects Utah school enrollment will rise by more than 9,700 children.

"This is the beginning of the boomers' grandchildren," Murphy told the Deseret Morning News. "And off we go."

The Oct. 1 head count for Utah schools puts the state's enrollment at an unprecedented 495,682 students. That's a 1.8 percent increase from last year, and about 1,500 more than projected, Murphy said.

The growth is attributed to birthrates and in-migration. Some 2,585 students who came from out of state took their seats in Utah classrooms, double what the state had anticipated.

But some of the growth is from neither babies nor out-of-staters.

It's from private- and home-schooled children opting for charter schools, Murphy said.

Charter schools, which aim to offer educational choices within the public school system, nearly doubled in enrollment for the second consecutive year. Charter schools enrolled 6,237 students, a 91.7 percent increase from last year. They're expected to hit the 10,000 student mark next fall.

"I just think it is evidence that one of the things parents want in this state is choice," said Eric Smith, State Charter Board member.

Alpine and Washington school districts posted the biggest enrollment gains.

Alpine took in 1,707 new students from last year, bringing its total to 52,825 students. That's a 3.3 percent change. The district also is projected to take in 2,384 kids next year, or 4.5 percent growth.

"We project we'll grow by another 8,000 to 8,500 kids in the next five to six years," spokeswoman Jerrilyn Mortensen said.

The district recently announced it would build three elementaries to open in fall 2006, using its last building-bond money. It is looking at options to educate new enrollees after that, from portables to bigger classes to another bond.

"We are . . . trying to get a feel for how big we're going to be," Mortensen said.

The Washington County School District is juggling growth in unexpected places that brought 1,267 new students — a 6.2 percent increase from last year, said Marshall Topham, assistant superintendent who oversees secondary schools and enrollment trends.