Study Questions Voucher Impact : Education: Passage of initiative would mean minimal loss of public enrollment because private schools are nearly full, report says. Backers of plan term the study biased.

The school voucher initiative on the 1994 statewide ballot could have far less impact than both sides claim, mostly because California’s private schools are so full that they could accommodate only about 43,000--less than 1%--of California’s public school students, a study has found.

The initiative would give parents of school-age children vouchers worth about $2,600 per child to apply toward private or parochial school tuition. Advocates say the change would force public schools to improve through competition with private schools, but opponents fear it could sweep thousands of children--and the public funding that accompanies them--out of a school system already reeling from years of budget cuts.

The federally funded survey of the state’s private schools by the Southwest Regional Laboratory found that 75% would be likely or very likely to accept students transferring from public schools, but most are already operating at or near capacity.

Although many schools said they would expand classroom space to accommodate transfers, it would take a “phenomenal expansion” or the reopening of many closed Catholic schools to create openings for even as few as 4% of California’s 5 million public school students, the report said.

“We conclude it is well beyond the capacity of existing private schools to accommodate so many students. . . . Therefore, a statewide voucher program will not significantly affect public school enrollment,” said co-authors Marcella R. Dianda and Ronald G. Corwin.

Backers of the voucher initiative attacked the study as biased and incomplete. Kevin D. Teasley, executive director of Excellence Through Choice in Education League, accused the researchers of bias, noting that Southwest Regional Laboratory’s board of directors is dominated by public school officials. Much of the educational establishment has adamantly opposed the initiative.

“It’s an outrage,” Teasley said. “They are presenting themselves as nonpartisan, and they obviously have an agenda.”

Questionnaires were mailed to 2,717 private schools eligible to participate in the proposed voucher program (schools with 25 or more students), and 1,004, or 37%, responded. Corwin said the respondents were a representative sampling of the state’s private schools.

The report appeared to confirm one fear of voucher opponents--that the measure would make private schools available to a “select group of public school students,” the report said.

Private schools told the researchers that they are unlikely to lower their admissions standards to include more low-achieving students. They tend to enroll fewer special education or limited-English-speaking students than public schools, the report said.

The researchers found that private schools charging low to moderate tuition (up to $4,999 annually) are more inclined to accept public school students and have more space for them than schools charging more than $5,000 a year.

The study also found that:

* Catholic and other religious schools are more inclined than non-religious schools to accept voucher students, but they also tend to be fuller: More than half are running at 95% capacity.

* Sixty-two percent of schools willing to accept students with vouchers charge less than $2,600 per year. But 40% of those schools said they would increase their annual tuition if they participated.

* Schools most likely to be open to voucher students have larger classes than other private schools, often as many as 32 students per class.