The Montgomery County Council tentatively voted yesterday to increase the property tax rate next year, but by an amount that would not keep pace with inflation.</br></br>The plan, which will be debated for months to come, would result in a 3 percent budget increase for the fiscal year that begins next July. County school officials say the plan would not provide enough money to maintain existing programs, let alone provide a pay increase to all teachers.</br></br>Montgomery real estate values have sagged to the point that the county's property tax revenue will fall nearly $26 million behind inflation next year if the current tax rate remains unchanged.</br></br>The council, in a decision that it can override next spring, yesterday voted 8 to 1 to increase the property tax rate by less than 2 percent, or 4.4 cents per $100 of assessed value. The basic prop-</br></br>That would generate about $12.7 million in additional revenue, or half the amount needed to keep pace with expected inflation.