The figures show a pound;700 difference in the amount delegated per primary pupil last year and a pound;500 difference in the amount delegated per secondary pupil between the lowest spender (Denbighshire) and the highest spender (Ceredigion).
And there are big differences in the proportion of their schools budget that authorities passed down to heads, from nearly 84 per cent in the Vale of Glamorgan to just over 75 per cent in Powys.
Alun Jones, director of NAHT Cymru, described school funding in Wales - where there are no government guidelines on what authorities should spend on education - as "a total lottery".
Too many LEAs were tying up urgently needed resources in bureaucracy, he said. He called for a Welsh national funding formula to deliver the agenda drafted by the Welsh Assembly.
The results of the NAHT's survey contrast with the figures for English education authorities released last week. These showed that English LEAs have passed on pound;385 million more to schools in the past year.
Only one of the 150 English authorities - Cornwall - has failed to meet the Government's target of giving heads control over at least 80 per cent of the money intended for schools.
She praised LEAs for passing on the extra pound;91m the Government had allocated to education in Wales in the current year. But she too criticised the wide variation - 34 per cent - between spending per pupil in the highest and lowest spending authorities.
The NAHT survey provides evidence that some Welsh LEAs are still very reluctant to relinquish detailed control of spending. Light bulbs and window cleaning are among the factors used to delegate funding to schools.
Welsh heads are especially concerned that money destined for the current pay reforms will not get through to schools.
"The LEAs say they have not had the extra money and the Welsh Assembly says they have," Alun Jones said. "I can see this leading to a serious confrontation."
The Assembly and the Welsh Local Government Association are consulting on proposed reforms to local authority funding in Wales. There are no plans to abandon the block grant but it is proposed that more emphasis should be given to social deprivation and to population sparsity.