The Board of Education on Tuesday will consider a ban on preferences in admissions to charter schools. (Barbara Davidson / Los Angeles Times)

Two popular Los Angeles charter schools have allowed some families to bypass a lottery for admission in exchange for providing special services or a substantial volunteer commitment.

The practices of Larchmont Charter School and Los Feliz Charter School for the Arts have raised concerns that such preference policies, if allowed, could open the door to well-connected friends or wealthier families who promise to contribute. In effect, critics say, charters could end up functioning more like private schools than campuses almost entirely supported with tax dollars.

Neither school concealed its enrollment procedures and they