Two separate studies out Wednesday by nonprofit groups dig into preschool programs in California - mostly bringing good news.

The American Institutes of Research (AIR), a national non-profit, conducted surveys, interviews and focus-groups to examine how "transitional kindergarten" fared in its first year in California.

The program, launched in 2012, is only open to children who turn 5 in the fall, just missing the cutoff for kindergarten. School districts had to offer at least one T.K. class, but not every school had to offer it. 

Researchers compared what was happening in T.K. classrooms to preschools nationwide and to current and past kindergarten classrooms.

They found it was broadly offered but implementation varied widely. That's because the state did not provide curriculum, rather schools and districts had to develop their own teaching plans.

"A lot more guidance will need to be provided if this is to be expanded to serve all 4-year-olds because there will be a wider range of developmental levels in a classroom," said Karen Manship, the lead researcher on the study.

The California Department of Education has provided very little data on the first year of T.K. statewide so the study gives a rare look at how it fared.

Manship said teachers reported teaching art, music, social studies and science at higher levels than traditional kindergarten classes - but not as much math or language arts.

"In many ways it looks like T.K. now in California looks a lot like Kindergarten used to 15 years ago," she said. 

The study found that 89 percent of districts offered the new grade and the demographics of the students mirrored the current kindergarten population, suggesting it was broadly offered.

About half of transitional kindergarten students were Latino, two thirds of were low-income and just under half were English Language Learners.

Researchers also found a large majority of transitional kindergarten teachers had prior experience or credentials in early childhood education.

RELATED: Will California expand T.K. to all 4 year-olds?

The group did not determine whether transitional kindergarten is adequately preparing students for kindergarten. It's evaluating that now. 

A second report released today looked at assessment data from over half of the state's Head Start participants and found two years of the preschool program "significantly increases the probability that a child is prepared for Kindergarten."

The study, conducted by the California Head Start Association and CCR Analytics, a firm specializing in child development data analysis, found two years of head start:

• "Increases the probability by 38% that a child demonstrates impulse control behaviors such as entertaining herself while waiting for a toy that another child is playing with."
• "Increases the probability that a child will meet age appropriate expectations [in math] before entering Kindergarten by 39%."

Researchers studied the 2013 child assessment results of 50,000 children from 81 Head Start programs statewide, more than half of California's Head Start population.