SAT scores at the Martha’s Vineyard Regional High School have dipped below the Massachusetts average, according to a report submitted to the high school committee this week by guidance director Michael McCarthy.

Average scores for the class of 2007 were several points under state levels in critical reading and math, while writing scores were 13 points below, Mr. McCarthy told the school committee in his report. Vineyard students performed better than the New England average in all areas except writing, where they trailed by a point. Island students performed above the national average in all fields.

Vineyard high school students posted average SAT scores of 518 in math, 509 in critical reading and 498 in writing. Average state scores were 522 in math, 513 in critical reading and 511 in writing. Average New England scores were 506 in math, 504 in critical reading and 499 in writing. Average national scores were 515 in math, 502 in critical reading and 496 in writing.

Falling SAT scores are part of a several-year slump for the high school and come during a national downturn in scores, which began in 2005 and for which there is currently no accepted explanation. Last year the national average dropped 10 points; traditionally there has been only a nominal variance in scores from year to year.

Some educators believe that significantly longer test times following the addition of new writing sections has led to burnout. However the College Board, which administers the national exam, tested for fatigue in field trials and found it was not a significant factor. The SAT — or its counterpart, the ACT (used more commonly in the Midwest), is required for entrance to most colleges and universities.

The nationwide trend does not explain the Vineyard high school’s drop below the state average. In his report to the school committee this week Mr. McCarthy said he sees the dip as a natural variance. “Looking at a longitudinal study, we actually see a jump in the math score and a dip in the reading and writing score, which occurs on occasion from class to class,” Mr. McCarthy wrote.

High school principal Margaret (Peg) Regan said this week she feels it is too soon to judge the scores. Referring to the new writing sections, Mrs. Regan said the change factor must be discounted before any ongoing trend can be considered. “With any significant change in a test like this, you see lower scores for the first and second year. Students and teachers have to become accustomed to the tactical ways to tackle a test,” she said by telephone yesterday. “When the first four-minute mile was run, it was big news around the world, that a human had accomplished such a feat. But people continued to break that record, not because they had bigger muscles or increased fitness, but because they became accustomed to the race.”

Also at the meeting on Monday the school committee discussed an ambitious proposal to float a bond issue to pay for two unrelated capital projects: a new fleet of buses and a new wastewater treatment system for the school. The plan, sketched by assistant to the superintendent for business affairs Amy Tierney, requires a general obligation bond of $2.4 million to simultaneously finance the two ventures. The wastewater treatment project is expected to cost $1.4 million.

Some school committee members expressed concern over the timeline, which calls for a wastewater plan to be finalized before December and envisions construction as a three to four-month project. As a municipal venture, the wastewater system is required to be advertised for competitive bidding.

The bond issuance cost is $35,000, a fee Ms. Tierney said she is anxious to avoid paying twice. “The bus project must keep going and if we have to, [come June] we’ll only be borrowing enough to buy the fleet,” she said when reached by telephone after the meeting. “But we will have to reapply for a separate bond for the wastewater at a later date.”

Committee members are resolute on the need for the new waste management system. “We can’t put any extra toilets in at the moment,” said high school principal Margaret (Peg) Regan on Monday night. “[The system] is imminent and necessary,” she said.

The waste treatment system is also intended to benefit the YMCA of Martha’s Vineyard, which plans to build a 48,000-sqare-foot center on land across the Edgartown-Vineyard Haven Road owned by the high school. Under the terms of its approval by the Martha’s Vineyard Commission, the YMCA is required to treat its wastewater. The start date for the $14 million YMCA project has been pushed back to the fall of 2008 due to funding issues.

The Y is expected to contribute to the cost of the treatment facility, but there is no signed agreement between the two entities that spells out financial responsibilities. On Monday night, Ms. Tierney outlined bond terms that limit financial contribution from a privately-owned company to 10 per cent. The school committee discussed the possibility of user fees after the fact, but superintendent Dr. James H. Weiss suggested the bond and YMCA involvement should be approached as distinct issues.

“The way to look at it this: the high school has a wastewater issue — we have a solution and we’re going to bond it” Mr. Weiss said, adding: “A separate issue comes along with the YMCA and for that we can have a tie-in fee.”

The plan calls for hooking the high school into the Oak Bluffs treatment plant and channeling wastewater to the leaching field under the school athletics track. The town wastewater commission has given the project a green light; approval is still needed from a brace of other local permitting authorities. Expenditure on the bus fleet replacement also needs final budget approval from member towns. Transportation and land use subcommittee meetings are both slated to take place later this month.

According to Ms. Tierney’s timeline, the bond request will go before the school committee for approval in December. If approved, it enters a 60-day waiting period, when member towns can object to the borrowing. Finally, if approved, the bond will come into use on June 15 next year with an initial payment of $500,000 due in 2009. Smaller payments will continue for the next 14 years.

Also on Monday the school committee reviewed a draft high school budget for fiscal year 2009, showing an increase of just over two per cent. A vote to certify the budget is set for early December.