A major enrollment miscalculation on the part of Manchester schools means the city is asking Hooksett for nearly $250,000 more in high school tuition costs for the 2007-08 school year.

And that means most of the projects Hooksett planned for improving local schools will be put on the back burner.

“We sort of got hit with this by surprise,” Dr. Charles Littlefield, superintendent of SAU 15, told the Hooksett School Board last night.

Hooksett sends its students to Manchester high schools -- this year, that number is 512 students.

Contractually, Hooksett pays a tuition fee per student, a figure that gets reconciled each year. For the past three years, Manchester has divvied out an annual credit to Hooksett, anywhere from $147 to $278 per student.

Now the tables have turned dramatically.

The initial estimate for Hooksett this year was a per pupil cost of $7,100, a $200 increase over the last year. But Manchester told Hooksett lower-than expected enrollment -- with no decline in costs -- has upped that figure to $7,584.32 per pupil, an increase of $484.32 per student.

Littlefield attributes the miscalculation to a number of factors, mostly the new high school in Bedford. He also cited general enrollment declines across the state and Hooksett students who attend high school outside of Manchester.

“The Bedford pullout, honestly, was probably the most difficult to predict,” Littlefield said.

This year, Bedford High School has 588 students in ninth and 10th grades. Next year, the enrollment is expected to jump to 959 students with the addition of 11th grade.

Manchester Mayor Frank Guinta said the city has lost 1,500 students over the past four years.

His $276 million budget proposal slashes education spending in the city by $7.3 million.

Instead of waiting until October, when Manchester and Hooksett typically reconcile their high school enrollment figures, Manchester is asking if Hooksett can pay the shortfall now -- a total of $247,971.84.

“We think we can pay a healthy part of this,” Littlefield said last night. “Our hope is to pay all of it and start the school year on solid ground.”

But that means four local projects won’t get done in Hooksett because the board hoped to pay for them with leftover budget funds. Postponed projects include a traffic study at Underhill School, additional lighting at Cawley Middle School, installing cameras on school buses and putting in two means of egress at the elementary schools.

The district promises to complete the projects approved by the voters on this year’s warrant, including a technology upgrade and a new maintenance van.

Littlefield said he also plans to turn over $130,000 to the town as promised for health care costs saved under the new teacher contract.

The increases for Hooksett aren’t over, as Manchester has also revised tuition estimates for 2009. In 2009, the estimated per pupil student cost is $7,990.22.