A proposed tax exemption for La Salle Academy in Providence was scaled back Tuesday before passing the Rhode Island Senate over the objections of some Democratic lawmakers. La Salle sought the exemption after receiving a property-tax bill, the first in its 150-year history, for part of its 26-acre Mount Pleasant campus last year. It was one of two private schools identified by Providence Mayor Jorge Elorza's administration last year as falling outside blanket exemptions in state law and without its own special exemption. If the La Salle bill is signed into law, the only other private school known to be facing a tax bill would be Community Preparatory School in South Providence.