The contrast is stark: TERRA Environmental Research Institute, which opened in 2009 and is one of Miami-Dade’s newest schools, boasts wireless Internet, interactive boards and 350 computers in labs — plus the personal laptops and tablets students are encouraged to bring.

At Coral Gables Senior High, where the oldest building dates back six-plus decades, 180 teachers share five interactive boards. Thick concrete walls disrupt wireless Internet in the main office. And the most high-tech classroom has a projector jerry-rigged to a DVD player and five Mac computers, partly paid for by candy sales.

And hardware isn’t even the biggest tech problem at Gables High.

“The issue we have is the network infrastructure,” said Principal Adolfo Costa, whose golf cart ride across the 26-acre campus spans buildings from 1948 to 2005.

Upgrading the digital network across Miami-Dade County Public Schools is a big piece of the spending plan for a $1.2 billion bond issue before voters on Nov. 6.

“It’s critical for us. We can’t move ahead with our goal of providing digital instruction without an upgraded infrastructure,” said Sylvia Diaz, the district’s administrative director of instructional technology.

Every Miami-Dade classroom would also get some kind of interactive device, like a SMART board, under the preliminary plan.

Many educators say the digital boards make class more visual, allow multimedia-rich lessons and keep the attention of students, who can touch and manipulate the screen.

Changing times

In recent years, Superintendent Alberto Carvalho and the School Board have made changes to bring education to the digital age. The district raised funds to apply for federal money to make all schools wireless. Starting this year, students are permitted to bring laptops, tablets, smartphones or other gadgets to class, under the new “Bring Your Own Device” policy. More schools are offering the iPrep magnet program, which blends online and traditional learning. And teachers are allowed to use videos on YouTube.

But without an upgraded network, Diaz said, students who bring devices to school can’t use them very well. Hundreds of students logging on at the same time for a video lesson could crowd the bandwidth.

The bulk of the money from the bond would go to renovate or replace many of the district’s aging school buildings. Diaz estimated about $47 million would be spent on interactive classroom technology, like SMART boards and smart projectors. Another $69 million would go to upgrading the information network.

The total bill is actually higher for the network — $139 million — but the district has raised about $7 million, which could increase to $70 million through the federal E-rate program for school connectivity.

The district’s budget for computers is $3.5 million this year, with less than $1 million for support.

If the bond issue is approved, the money would be repaid through property tax revenues over 30 years, essentially continuing the 1988 bond, which ends in five years. For the first year, 2013, the average homeowner would pay $5 per $100,000 of assessed value for the new program, in addition to the $23 for every $100,000 of assessed value for the existing bond program. For the full term of the new program, a homeowner would pay an average of $27 for every $100,000 of assessed value, up to the maximum of $35.