It’s hard to argue against lower class sizes, which is what Initiative 1351 says it would provide.

The latest figure finds Washington ranks 47th for classroom size in the U.S., a ranking disputed by the initiative’s opponents. But even factoring in the effect of recent spending for K-3 classes, the state’s ranking likely hasn’t lifted out of even the bottom third.

I-1351 seeks to mandate the hiring of 7,400 teachers statewide, giving districts the ability to lower the average number of students to 17 from the current 25 for each kindergarten through third-grade teacher, and to 25 from the current 28 for each teacher in the fourth through 12th grades. Ratios would be even lower for schools where 50 percent or more of the students receive free or reduced-price lunches. The initiative also extends spending outside the classroom to require the hiring of about 18,000 other school workers, including principals, librarians, teacher’s assistants, counselors, nurses, custodians, IT workers and other support staff.

Here’s where the initiative’s flaws start to outweigh its good intentions:

While the initiative would hire more teachers, it provides no funding for additional classroom space, improving the student-teacher ratio but not the classroom squeeze for some schools. Those who vote for I-1351 have to know that more funding from the state and through school district bonds will be necessary to provide the space needed for additional classrooms for more teachers.

The state Office of Financial Management puts the initiative’s costs at nearly $5 billion through 2019. The initiative provides no funding source, leaving that decision to the Legislature, which at the same time must find funding to satisfy the state Supreme Court’s McCleary ruling to fully fund education, pegged at $1 billion to $3 billion each for the next two bienniums.

Supporters say I-1351 actually helps the state meet its goal of fully funding education, but it’s certain more will be needed beyond the addition of employees. Opponents, including the League of Education Voters, which wrote the first class-size initiative, I-728, in 2000, are concerned that I-1351 could actually result in a loss of funding for areas such as early education and college preparation.

Passage of I-1351 looks probable with the support of 61 percent of likely voters, according to the latest Elway poll. If the Legislature wasn’t impressed when the state Supreme Court held it in contempt earlier this year, it’s about to feel the contempt of the voting public, assuming I-1351 passes and leaves it to sort out how to fund it and satisfy the McCleary mandate.

While the Legislature has been frustratingly slow to fully fund education, it should be allowed to continue that work without the distraction of funding I-1351.

It’s aggravating to argue against a measure that would lower class sizes, but The Herald Editorial Board cannot support an initiative that is ill-timed and liable to create unintended consequences.