LYNN – School Superintendent Catherine Latham slammed a local charter school for sending problem students to city-run schools one day after a state board gave the Knowledge Is Power Program permission to add kindergarten through fourth grade classes.Latham fired off statistics and criticized KIPP Executive Director Caleb Dolan?s claim that the charter school won permission to expand partly for its ability to retain students.?We keep our kids,” said Dolan.Not so fast, Latham shot back Tuesday, pointing to School Department statistics showing 47 KIPP students returned to Lynn schools during the current academic year, and 55 others left the Highlands charter school for Lynn schools in the 2012-2013 and 2013-2014 school years.?They don?t necessarily keep their students,” Latham said. “They transfer students who are problematic back to the Lynn schools.”Wrong, replied Dolan. He cited state statistics that indicate KIPP?s attrition rate is lower than data for Lynn public schools. KIPP?s attrition rate was 4.6 percent in 2014 – lower, said Dolan, than any Lynn school except Lynn Woods (2.8).The two educators waged their numbers war a day after the state Board of Elementary and Secondary Education voted 8-2 Monday in favor of KIPP?s proposal to add five new grades, beginning with a 120-student kindergarten, over the next five years.By 2020, the charter school intends to offer a kindergarten through 12th grade education with middle and high school students attending classes in KIPP?s Highlands school and the youngest students attending school in a yet-to-be-chosen site.?This is huge,” KIPP spokeswoman Colette Sanborn said. “It?s an opportunity to take students all the way through to college.”In evaluating KIPP?s expansion plans, state educators noted the school crafted a student recruitment and retention plan in 2010 and “made significant gains in the recruitment of English-language learners.”Sanborn said new students entering KIPP have needed “remediation” to bring their skills up to KIPP learning levels. But Lynn Teachers Union President Brant Duncan said KIPP does not educate a student population comparable to the more than 15,000 students enrolled in Lynn public schools.?To earn the right to expand, a charter school must demonstrate its value to the larger community and to the full array of students and families who comprise that community,” Duncan said. “Based on their track record to date, KIPP does not pass that test in Lynn.”In a little more than 11 years, KIPP has grown from a small band of teachers educating fifth-graders in space leased from Holy Family Church to a $25 million new school building with a panoramic view of Lynn.Based on a national charter education model with the motto “Work hard. Be Nice,” KIPP won local support, with Swampscott residents Joel and Mary Abramson becoming donors in 2007, the same year the academy had 320 fifth- through eighth-graders enrolled in classes.By 2010, the school set its sights on building in the Highlands on a large parcel of vacant land surrounding a veterans post.The Abramsons donated $50,000 to KIPP Lynn in 2011. State educators noted improvements in KIPP?s student test scores between 2012 and 2013 – the same year school officials unveiled plans to expand to a kindergarten through fourth grade program.Latham tried unsuccessfully in late 2014 to convince state educators that KIPP?s expansion places Lynn schools in competition with the academy for limited space for new schools.Dolan Monday said initial space for the kindergarten program will be secured by March 30.?We have a couple of good candidates,” he said, concerning the space search.Latham acknowledged Tuesday that Lynn schools “have received some excellent students from KIPP as well.” But Duncan said charter schools should receive scrutiny from local as well as state education officials.?We?re pursuing legislation to give authority to create, expand and renew a charter with the local school committee,” he said.