Gregory, my son, saved the life of Beasley, my cat. Two Iowa co-eds confronted a dorm rule prohibiting pets. What to do?

“My Dad will take Beasley,” Gregory offered.

Scratches from this kitten turned my arms bloody. Beasley would have to go, I protested.

To which Gregory replied, “Dad, if you’re going to have a cat you’re going to have scratches.”

After 12 years’ behavior modification efforts Beasley very seldom scratches. Now he bites.

We live with other realities of this kind.

Exercise consumes calories. Eating stores calories. Eat 3500 calories more than you expend and you gain a pound.

Live on 90 percent of what you earn, invest the difference over a lifetime, and ultimately retirement’s manageable. Live on 105 percent of what you earn and ultimately bankruptcy’s inevitable.

The problem is we want it all.

We want to have the cat and not get scratched, eat and not gain weight, spend and still gain wealth.

So it is with overcrowded classrooms and schools. We want our kids to go to the closest school, but to find identically-sized classrooms once they get there.

Think about it. It’s basic math.

With 13 grades (K-12), and 10,500 students, that’s about 800 per grade. For simplicity, assume our 17 elementary schools have 40 classrooms available for kindergarten. That’s an average of 20 students per classroom.

So long as students show up at schools each fall in groups of 20 there is no problem. Every classroom has 20 kids.

The problem is, they don’t. They come one at a time. Our district-wide population projections are much more accurate than those for each school.

If 28 kids show up, instead of 20, why don’t we just split the group into two classes of 14 and hire another teacher?

More basic math. Teachers cost about $50,000 each (including benefits), and almost everyone wants to increase that. With 750 teachers, that’s already $37.5 million. Most things schools pay for are required by law. Like busing and school lunches. Those we could abolish, such as athletics, we won’t.

The law caps what we can raise and spend. We can’t run deficits and we can’t print money.

So we can’t just hire another teacher.

There is an alternative. Many use it, including the well-regarded West Des Moines District. There are lots of variations.

It’s really pretty simple. Kindergarten registration is by school district, not building. Count the available kindergarten teachers, classrooms and students. Divide one by the other. Assign students so that number becomes the cap on students per classroom.

Every kindergarten has exactly the same number of students.

Once in, they’re guaranteed K-6 in that school. But any student who later transfers into a higher grade gets assigned to the school with the smallest class.

Lots of variations are possible.

• To ease transfers, neighboring schools can be clustered. Three or four buildings operated as one school with a distributed campus. One faculty. Joint activities. Joint PTO.

• Students now enrolled could be grandfathered.

• The cap can be a range (as in Des Moines).

• Different counts for special needs students.

• Triggers for additional associates.

But research supports the idea that class size – especially K-3 – makes a difference.

We can’t have it all.

Two days from now we register next fall’s kindergarten students – in a way that perpetuates inequity.

Because if you’re going to have a cat you’re going to have scratches.

And if you’re going to let students show up willy-nilly at elementary schools you’re going to have grossly disparate class sizes.

There are alternatives.

We can reject them. That’s our choice. But that refusal to change inevitably creates another year of legitimate complaints about class size.

Nicholas Johnson is an Iowa City School Board member. More information is available on his Web site www.nicholasjohnson.org.