Arlington School Superintendent Larry Cuban last night proposed a $48.4 million budget that would give the county's school employes, including its 1,000 teachers, raises averaging 7 percent in the next school year.

But the pay proposal, in which each employe would get at least a 5.3 percent raise, was denounced as unsatisfactory by George Long, and official of the Arlington Deucation Association, the conty teacher organization. He said it really amounts to only a 3.4 percent cost-of-living increase since, unlike recent budgets, it includes raises owed for length of service.

"This just puts us farther behind, because of inflation, than we've ever been," Long said.

Cuban emphasized that his pay proposal meets the Carter administration's voluntary wage guidelines.

The school board is under pressure from the County Board, which funds school operations, to hold the line on spending. Cuban's budget exceeds by nearly $1 million the amount tentatively allocated by the County Board, a sum that Cuban repeatedly has criticized as inadequate.

The deucation association had asked for 18 percent salary increases, which would have added $3.5 million to the budget. Arlington teachers have been given a 7 percent raise over the last two yrars.

Cuban's budget proposal is 3 percent and nearly $2 million higher than the current $46.5 millioj spending program.

It recommends modest program improvements, including reducing first grade class size from 24 to 20 pupils and expandin a basic skiils program for those minotity students who failed state-mandated minimum competency tests last year.

The budget projects an enrollment decline of nearly 5 percent, and mentions the possibility of cutting 61 teching and administrative positions.

It calls for receiving $38.9 million form county funds and the remainder from state and local sources. Schools are the largest single expenditure in Arlington's budget, with 80 percent of the school gudget funded by county tax dollars.

Teacher pay raises of 5.5 percent have been proposedin Fairfax County, 5 percent in Montgomery County, and 3.3 percent in Prince George's County.