Summer school -- two words normally dreaded by students and usually considered a punishment for those who failed during the year – is becoming increasingly popular in Toronto.

Enrollment in summer school classes over the past few years at the Toronto District School Board (TDSB) has been steadily increasing.

In 2010, there were 22,709 students from both the secondary and elementary school levels registered in summer school classes. That number increased slightly in 2011, with just over 23,000 students enrolled in classes.

And this year, over 25,000 students are hitting the books, giving up a part of their summer vacation to earn extra credits.

Colin Russell is one of those ambitious students.

The 16-year-old, who plans to become an engineer, said although summer school is “kind of a bummer,” he’s willing to sacrifice part of his two-month summer vacation to get ahead.

"A lot of students like me are fast-tracking for next year," Russell told CTV Toronto.

And despite the fact that some Toronto schools, such as York Mills Collegiate Institute, are not air conditioned, many students admit they enjoy the extra school work.

"It’s actually pretty fun. It’s better than staying home,” said Alekia Gouda, who wants to be an architect when she finishes school. “I have a brother who’s home and he said it’s boring."

But it’s not just ambition and a desire to learn that’s motivating students to give up a part of their summer.

According to Karen Falconer, the executive superintendent at the TDSB, the number of students electing to take summer school classes has increased due to the shorter amount of time spent in secondary school. In 2003, the province phased out the Ontario Academic Credit, reducing the number of years in high school from five to four.

"(Students) don’t get to take a variety of courses," Falconer said. "So night school and summer school become even more important."

The board has also increased the number of courses and sites where summer school is being offered, making it easier for students to attend classes. This year, there are 21 sites across the city where summer school is being offered. Last, there were only 13 sites.

Summer school is paid for by the province and runs in July.

In York Region, there are 15,000 students enrolled in summer school and close to 12,000 in Peel.

With a report from CTV Toronto's Naomi Parness.