FREMONT -- With a low crime rate, high-quality schools and a growing tech sector in an improving economy, Fremont has caught the eye of covetous home developers.

But several residential developments soon will add thousands of students to already overcrowded campuses, which school leaders say could damage the quality of education, strain district resources, send students out of their neighborhoods and add to traffic as parents drive kids to those more distant schools.

District leaders say they are close to a crisis point.

And even though it is likely developers will largely finance one new school, the leaders also want voters to approve a $650 million school bond -- Alameda County's largest ever -- on the June ballot to ease existing and anticipated overcrowding. That has some parents saying developers should start paying much more in development fees to Fremont Unified, so that property owners aren't burdened with more tax debt.

"I don't think it would be fair to saddle taxpayers with costs for a new school," Fremont resident Mary Biggs said. "You can't constantly turn to the taxpayers."

Forest Park Elementary's overcrowding reflects the district's challenge, said Superintendent of Schools James Morris. Its 982-student enrollment is well above the ideal maximum, 850 students, for an elementary campus. But it could be worse, as another 215 neighborhood students who normally would attend Forest Park attend other campuses outside their area, district leaders said.

Several other schools are crowded in Fremont Unified, where 33,662 students attend 42 campuses. Enrollment has grown by 2,000 students in the past six years, and 1,500 more are expected by 2017. The district has added portable classrooms as a short-term solution, but it is running out of room, Morris said.

"It's a problem, and we don't have the capacity to solve it," he said. "We just can't continue like this because we don't have the seats available for more students."

And it might get worse before it gets better.

The district is lowering class sizes from 30-1 to 24-1 for grades K-3, over a four-year period to comply with new mandates for state funding under Proposition 30. Smaller class sizes are better for children, but they force schools to use more classrooms, Morris said.

"It's good pressure to reduce class sizes and increase enrollment," he said. "But with the two pressures, we're quickly approaching a point where we have no available classrooms."

Meantime, the City Council has approved 500 single-family residences at Patterson Ranch in Ardenwood, where Forest Park and other elementary schools already are overcrowded.

And even more new housing, and the students that likely will come with it, are on the way.

The Warm Springs/South Fremont development near the BART station opening next year would add 2,700 housing units. Warm Springs Elementary already has 951 students, so another elementary school must be built, district leaders said.

Developers should pay more money to provide the classroom space for the new students those developments will generate, says Kathryn McDonald, a longtime Fremont resident.

"We as citizens have to hold developers accountable for the impacts they're having," McDonald said. "If developers are not able to mitigate at least the school portion of their impacts to the city, then why approve their projects?"

Biggs, also a Fremont parent, said she wants developers to contribute more. New development is fine, she said, but the problem stems more from controlling the city's pace of growth.

"The city must pace its approval of new housing better," Biggs said. "Then the school district can catch up with it, and the increased revenues from growth will provide a natural flow into our school district's and city's general funds."

District and city leaders say that state law ties their hands when it comes to developers' contributions. The Leroy F. Greene School Facilities Act limits cities' ability to require developers to address their effects on schools.

Thus, Fremont Unified's collection of school impact fees is the only mitigation that can be imposed, said Fremont Planning Manager Kristie Wheeler.

State law allows Fremont to charge developers $5.27 per square foot for new residential development. That's considerably higher than Milpitas, which charges $3.36 per square foot, or Union City, which charges $3.27. Builders in Sunnyvale, a South Bay city with a population two-thirds that of Fremont's, pay $1.98.

Fremont's pricey land values, and the district's low availability of classrooms and high number of portable classrooms are some of the factors in the state's formula allowing Fremont to charge higher development fees, Morris said.

But the fees go only so far. Just building an elementary school in Ardenwood could cost as much as $40 million, and developer fees from Patterson Ranch, for example, are estimated at $6 million to $7 million.

That disparity means Fremont Unified must do a good job of educating the development community about the schools' needs.

"We want them to understand that if they contribute up front to building a new school when planning a development, that makes the houses worth that much more when they sell them," Morris said.

Messages left Friday seeking comment from developers involved in Fremont projects were not returned.

Some Fremont taxpayers, such as Biggs and McDonald, want developers to pay for all or most of the cost of a new Warm Springs school.

They might get their wish, said Fremont Mayor Bill Harrison, who said he expects the development community to "basically furnish the district with a school in Warm Springs."

He added: "This is all being negotiated, but from my perspective, you won't see that project being approved without the school situation being addressed."

Contact Chris De Benedetti at 510-353-7011. Follow him at Twitter.com/cdebenedetti.