California State Teachers Retirement System board has purchased secondary interests in two Kohlberg, Kravis & Roberts leveraged buyout funds. It bought stakes of about $50 million each that the Long Term Credit Bank of Japan owned in the KKR 1987 and KKR 1996 funds. ``One of our objectives is to increase our participation in the market for secondary interests such as these, said Patrick Mitchell, CIO. He also reported the $101 billion Sacramento-based fund had heard the second of three presentations by Pension Consulting Alliance Aug. 3 regarding its biennial asset allocation study. PCA is working with Callan Associates and William M. Mercer on the study and will make the final presentation at the September board meeting, said Mr. Mitchell. "It looks like they will not be recommending substantive changes, from where were at now, he said.