Slow internet connections at schools are affecting pupils' ICT studies, according to education watchdog Estyn.
Its new report calls on Welsh ministers to provide adequate broadband links for all schools saying poor quality connectivity "hinders" class work.
The Welsh government said £39m is being invested in broadband and network infrastructure for schools.
Council leaders said some of the improvement work is due to be carried out over the summer holidays.
Estyn has published a report into the standards in ICT - information computer technology - in primary and secondary schools in Wales looking at its impact on pupils' learning.
Standards were "good or excellent" in half of the primary schools visited, the watchdog found.
However, Ann Keane, chief inspector of education and training in Wales, said despite some "positive progress, there is still work to be done".
The report found that while Wales' councils provide nearly all schools with an internet connection, around half the schools surveyed said slow connections were a problem making internet searches for a whole class difficult.
It added that the level of filtering and blocking of internet sites by local authorities - to ensure pupils stay safe while online - hindered class work "unnecessarily" in the majority of schools.
Report author Maldwyn Pryse said that using ICT to motivate pupils was working well and "having a beneficial impact on standards as well".
He added that there were examples of good practice where technology was also being used to stretch more talented pupils.
"We've one case study based on a school in Bridgend where they're working with more able and talented pupils to help them learn programming skills - so it helps thinking skills, team work and that again is having a positive impact on standards," he told BBC Radio Wales.
The Welsh Local Government Association (WLGA), which represents councils, said "digital learning" was a priority with a huge amount of work undertaken to ensure learners have "improved access to safe and secure broadband services".
A new Learning in Digital Wales Grant - announced in January by the Welsh government - sets aside £10,000 for primary schools and £20,000 for high schools to invest in ICT such as reliable broadband services.
"Much of this work has been planned to take place over the summer recess, and many learners and teachers will benefit from this investment during the next academic term," said a WLGA spokesperson.
"This is a great first step in improving connectivity and the ICT support provided to local schools in order to promote a culture of digital citizenship for learners in Wales."
The Estyn report wants more portable technologies such as tablet computers used in schools and more help for pupils who are "more able and talented to reach their potential".
The Welsh government said Estyn's report was "broadly positive".
"We will now work with local authorities, the education consortia and schools as well as our wider partners supporting schools in delivery of ICT within the curriculum to ensure the recommendations for further work are addressed," said a spokesperson.