Research on social capital in non-educational areas has been carried out by many experts, such as Bhandari & Yasunobu, Putnam, Coleman, and Paxton, etc. And, researches on social capital focused on educational institutions among others, carried out by Stoddart, Ju'subaidi, and Behtoui and Strömberg. They concluded that social capital is a determining factor in developing educational institutions. However, not all educational institutions are aware of this. This study aimed to analyze the social capital used by SMP Al-Irsyad Al-Islamiyah and SMP Putra Harapan Boarding School in Purwokerto which have succeeded in building their schools. Meanwhile, the collection method used is interviews, observation and documentation and then analyzed by collecting, reducing, and displaying data which ends with a drawing conclusion. The findings indicate that two institutions have the same model of bonding, bridging, or in trust building. However, Sample A is homogeneous exclusively and sample B is heterogeneous inclusive. The relationship built on Sample A is vertical, while Sample B is horizontal. Meanwhile, in building a branding image, Sample A uses the label of Al-Irsyad Islamiyah and in Sample B offers a boarding program that must be followed by all students. The trust development carried out by the two instutions has created a distinctive development identity in Islamic schools and it has become a good value in the society.