The authority unanimously approved a far-reaching Gaelic policy last month but is supporting official status against the backdrop of the crisis in teacher supply.
Bruce Robertson, Highland's education director, said the loss of a teacher at Morar primary would severely damage the success of Gaelic-medium education at the west coast school, which has been built up from half a dozen pupils to three classes.
"We will have to reduce that to two weeks' Gaelic-medium and two weeks'
English education," Mr Robertson said.
He described Gaelic-medium teaching as "very fragile" and told MSPs that legal status would remind teacher training institutions that Gaelic was "not peripheral". He knew of several students who had been turned away because universities had met their quota.
"The biggest single obstacle to the development of Gaelic is the lack of qualified teachers and we have recently helped Mike Watson, the Minister for Gaelic, to review the number. It was thought previously that we needed 20 trained teachers across Scotland but now we are looking at 30 each year for the next few years. Some youngsters are travelling 20 miles each way each day to attend a Gaelic class," Mr Robertson said.
Gaelic in Highland is a core activity and the council spends pound;1 million more than it receives in government grant. Some 45 schools are involved in Gaelic-medium education, with 1,100 pupils and 74 teachers. It is widely taught as a second language, while plans are developing for the first full school-community resource in Inverness, built through the public private partnership initiative.
Mr Robertson said it was "somewhat perverse" for Gaelic to be included in the national education priorities without enjoying the benefits of legal status.
There was further ammunition to fire at the Convention of Scottish Local Authorities after its senior education representatives refused to support the Bill. Helen Law, Cosla's education spokeswoman and education convener in Fife, angered MSPs and Highland councillors by opposing any further duties on councils that could lead to unspecified costs if they were forced to expand Gaelic provision for small numbers.
Ms Law said the proposed measures were "unwelcome", but Cosla was not against Gaelic or Gaelic-medium education. It should be up to councils to respond flexibly to local needs and demands without further imposition, she said.
Eric Gotts, Liberal Democrat education leader in East Dunbartonshire, said:
"The vast majority of councils in Cosla do not support the Bill."