Real estate investor ESJ Capital Partners focuses on office space, entertainment and hospitality but is expanding an asset class — charter school buildings.

“Education infrastructure is a growing niche nationally,” said chief investment officer Matthew Fuller.

ESJ, which has been investing in school buildings for 10 years, most recently sold two charter K-8 schools it developed with general contractor MG3 Developer Group LLC for a total of $44.99 million to affiliates of Charter Schools USA, a for-profit charter school manager. The deal closed March 22.